diff --git a/Cargo.lock b/Cargo.lock
index f5e59849d51..e8ff0776ed6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -13,23 +13,23 @@ dependencies = [
  "flate2 0.2.13 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "git2 0.4.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "git2-curl 0.4.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "glob 0.2.10 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "glob 0.2.11 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "hamcrest 0.1.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libgit2-sys 0.4.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libgit2-sys 0.4.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "log 0.3.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "num_cpus 0.2.10 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "regex 0.1.48 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "num_cpus 0.2.11 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "regex 0.1.58 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.18 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "semver 0.2.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "tar 0.4.3 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "semver 0.2.3 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "tar 0.4.4 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.4 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "term 0.4.4 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "time 0.1.34 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "toml 0.1.27 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "toml 0.1.28 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "url 0.2.38 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -37,16 +37,16 @@ name = "advapi32-sys"
 version = "0.1.2"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "winapi-build 0.1.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "aho-corasick"
-version = "0.4.1"
+version = "0.5.1"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "memchr 0.1.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "memchr 0.1.10 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -61,10 +61,10 @@ source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "cmake"
-version = "0.1.13"
+version = "0.1.16"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "gcc 0.3.23 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.25 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -87,10 +87,10 @@ version = "0.2.17"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "curl-sys 0.1.32 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "log 0.3.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.7.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "url 0.5.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "url 0.5.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -98,11 +98,11 @@ name = "curl-sys"
 version = "0.1.32"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "gcc 0.3.23 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.25 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.7.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "pkg-config 0.3.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -110,7 +110,7 @@ name = "docopt"
 version = "0.6.78"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "regex 0.1.48 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "regex 0.1.58 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.18 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "strsim 0.3.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
@@ -121,7 +121,7 @@ version = "0.3.2"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "log 0.3.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "regex 0.1.48 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "regex 0.1.58 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -129,7 +129,7 @@ name = "filetime"
 version = "0.1.10"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -137,13 +137,13 @@ name = "flate2"
 version = "0.2.13"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "miniz-sys 0.1.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "gcc"
-version = "0.3.23"
+version = "0.3.25"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -151,7 +151,7 @@ name = "gdi32-sys"
 version = "0.1.1"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -160,9 +160,9 @@ version = "0.4.2"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 0.1.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libgit2-sys 0.4.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "url 0.5.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libgit2-sys 0.4.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "url 0.5.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -173,12 +173,12 @@ dependencies = [
  "curl 0.2.17 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "git2 0.4.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "log 0.3.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "url 0.5.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "url 0.5.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "glob"
-version = "0.2.10"
+version = "0.2.11"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -186,7 +186,7 @@ name = "hamcrest"
 version = "0.1.0"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "num 0.1.30 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "num 0.1.31 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -194,27 +194,27 @@ name = "kernel32-sys"
 version = "0.2.1"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "winapi-build 0.1.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "libc"
-version = "0.2.7"
+version = "0.2.8"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libgit2-sys"
-version = "0.4.0"
+version = "0.4.1"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cmake 0.1.13 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "gcc 0.3.23 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "cmake 0.1.16 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.25 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "libssh2-sys 0.1.36 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.7.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "pkg-config 0.3.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -230,11 +230,11 @@ name = "libssh2-sys"
 version = "0.1.36"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cmake 0.1.13 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "cmake 0.1.16 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.7.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "pkg-config 0.3.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -242,9 +242,9 @@ name = "libz-sys"
 version = "1.0.1"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "gcc 0.3.23 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "pkg-config 0.3.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.25 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -252,7 +252,7 @@ name = "log"
 version = "0.3.5"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -262,10 +262,10 @@ source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "memchr"
-version = "0.1.7"
+version = "0.1.10"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -273,18 +273,18 @@ name = "miniz-sys"
 version = "0.1.7"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "gcc 0.3.23 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "gcc 0.3.25 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "nom"
-version = "1.2.0"
+version = "1.2.2"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "num"
-version = "0.1.30"
+version = "0.1.31"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "rand 0.3.14 (registry+/~https://github.com/rust-lang/crates.io-index)",
@@ -293,12 +293,10 @@ dependencies = [
 
 [[package]]
 name = "num_cpus"
-version = "0.2.10"
+version = "0.2.11"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "kernel32-sys 0.2.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -307,15 +305,15 @@ version = "0.7.6"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gdi32-sys 0.1.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "libressl-pnacl-sys 2.1.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "pkg-config 0.3.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "user32-sys 0.1.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "pkg-config"
-version = "0.3.6"
+version = "0.3.8"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -331,22 +329,23 @@ name = "rand"
 version = "0.3.14"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "regex"
-version = "0.1.48"
+version = "0.1.58"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "aho-corasick 0.4.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "memchr 0.1.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "regex-syntax 0.2.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "aho-corasick 0.5.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "memchr 0.1.10 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.3.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "utf8-ranges 0.1.3 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "regex-syntax"
-version = "0.2.2"
+version = "0.3.0"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -356,10 +355,10 @@ source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "semver"
-version = "0.2.2"
+version = "0.2.3"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "nom 1.2.0 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "nom 1.2.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -369,11 +368,11 @@ source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "tar"
-version = "0.4.3"
+version = "0.4.4"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "filetime 0.1.10 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -390,7 +389,7 @@ version = "0.4.4"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -399,13 +398,13 @@ version = "0.1.34"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.7 (registry+/~https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.8 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "toml"
-version = "0.1.27"
+version = "0.1.28"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "rustc-serialize 0.3.18 (registry+/~https://github.com/rust-lang/crates.io-index)",
@@ -436,7 +435,7 @@ dependencies = [
 
 [[package]]
 name = "url"
-version = "0.5.5"
+version = "0.5.7"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "matches 0.1.2 (registry+/~https://github.com/rust-lang/crates.io-index)",
@@ -451,10 +450,15 @@ name = "user32-sys"
 version = "0.1.2"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.2.5 (registry+/~https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.6 (registry+/~https://github.com/rust-lang/crates.io-index)",
  "winapi-build 0.1.1 (registry+/~https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "utf8-ranges"
+version = "0.1.3"
+source = "registry+/~https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "uuid"
 version = "0.1.18"
@@ -466,7 +470,7 @@ dependencies = [
 
 [[package]]
 name = "winapi"
-version = "0.2.5"
+version = "0.2.6"
 source = "registry+/~https://github.com/rust-lang/crates.io-index"
 
 [[package]]
diff --git a/src/cargo/ops/cargo_compile.rs b/src/cargo/ops/cargo_compile.rs
index ad82d4f773e..fa0ff05818b 100644
--- a/src/cargo/ops/cargo_compile.rs
+++ b/src/cargo/ops/cargo_compile.rs
@@ -469,7 +469,7 @@ fn scrape_target_config(config: &Config, triple: &str)
         None => return Ok(ret),
     };
     for (lib_name, _) in table.into_iter() {
-        if lib_name == "ar" || lib_name == "linker" {
+        if lib_name == "ar" || lib_name == "linker" || lib_name == "rustflags" {
             continue
         }
 
diff --git a/src/cargo/ops/cargo_rustc/context.rs b/src/cargo/ops/cargo_rustc/context.rs
index b350ba6efad..b400745644c 100644
--- a/src/cargo/ops/cargo_rustc/context.rs
+++ b/src/cargo/ops/cargo_rustc/context.rs
@@ -1,4 +1,5 @@
 use std::collections::{HashSet, HashMap};
+use std::env;
 use std::path::{Path, PathBuf};
 use std::str::{self, FromStr};
 use std::sync::Arc;
@@ -616,4 +617,54 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
         //       profile? How is this controlled at the CLI layer?
         &self.profiles.dev
     }
+
+    // Acquire extra flags to pass to the compiler from the
+    // RUSTFLAGS environment variable and similar config values
+    pub fn rustflags_args(&self, unit: &Unit) -> CargoResult<Vec<String>> {
+        // We *want* to apply RUSTFLAGS only to builds for the
+        // requested target architecture, and not to things like build
+        // scripts and plugins, which may be for an entirely different
+        // architecture. Cargo's present architecture makes it quite
+        // hard to only apply flags to things that are not build
+        // scripts and plugins though, so we do something more hacky
+        // instead to avoid applying the same RUSTFLAGS to multiple targets
+        // arches:
+        //
+        // 1) If --target is not specified we just apply RUSTFLAGS to
+        // all builds; they are all going to have the same target.
+        //
+        // 2) If --target *is* specified then we only apply RUSTFLAGS
+        // to compilation units with the Target kind, which indicates
+        // it was chosen by the --target flag.
+        //
+        // This means that, e.g. even if the specified --target is the
+        // same as the host, build scripts in plugins won't get
+        // RUSTFLAGS.
+        let compiling_with_target = self.build_config.requested_target.is_some();
+        let is_target_kind = unit.kind == Kind::Target;
+
+        if compiling_with_target && ! is_target_kind {
+            // This is probably a build script or plugin and we're
+            // compiling with --target. In this scenario there are
+            // no rustflags we can apply.
+            return Ok(Vec::new());
+        }
+
+        // First try RUSTFLAGS from the environment
+        if let Some(a) = env::var("RUSTFLAGS").ok() {
+            let args = a.split(" ")
+                .map(str::trim)
+                .filter(|s| !s.is_empty())
+                .map(str::to_string);
+            return Ok(args.collect());
+        }
+
+        // Then the build.rustflags value
+        if let Some(args) = try!(self.config.get_list("build.rustflags")) {
+            let args = args.val.into_iter().map(|a| a.0);
+            return Ok(args.collect());
+        }
+
+        Ok(Vec::new())
+    }
 }
diff --git a/src/cargo/ops/cargo_rustc/fingerprint.rs b/src/cargo/ops/cargo_rustc/fingerprint.rs
index 837b14bc113..042e223b3cb 100644
--- a/src/cargo/ops/cargo_rustc/fingerprint.rs
+++ b/src/cargo/ops/cargo_rustc/fingerprint.rs
@@ -111,6 +111,7 @@ pub struct Fingerprint {
     deps: Vec<(String, Arc<Fingerprint>)>,
     local: LocalFingerprint,
     memoized_hash: Mutex<Option<u64>>,
+    rustflags: Vec<String>,
 }
 
 #[derive(RustcEncodable, RustcDecodable, Hash)]
@@ -160,6 +161,9 @@ impl Fingerprint {
         if self.profile != old.profile {
             bail!("profile configuration has changed")
         }
+        if self.rustflags != old.rustflags {
+            return Err(internal("RUSTFLAGS has changed"))
+        }
         match (&self.local, &old.local) {
             (&LocalFingerprint::Precalculated(ref a),
              &LocalFingerprint::Precalculated(ref b)) => {
@@ -202,8 +206,9 @@ impl hash::Hash for Fingerprint {
             ref deps,
             ref local,
             memoized_hash: _,
+            ref rustflags,
         } = *self;
-        (rustc, features, target, profile, deps, local).hash(h)
+        (rustc, features, target, profile, deps, local, rustflags).hash(h)
     }
 }
 
@@ -222,6 +227,7 @@ impl Encodable for Fingerprint {
                     (a, b.hash())
                 }).collect::<Vec<_>>().encode(e)
             }));
+            try!(e.emit_struct_field("rustflags", 6, |e| self.rustflags.encode(e)));
             Ok(())
         })
     }
@@ -252,9 +258,11 @@ impl Decodable for Fingerprint {
                             features: String::new(),
                             deps: Vec::new(),
                             memoized_hash: Mutex::new(Some(hash)),
+                            rustflags: Vec::new(),
                         }))
                     }).collect()
-                }
+                },
+                rustflags: try!(d.read_struct_field("rustflags", 6, decode)),
             })
         })
     }
@@ -346,6 +354,7 @@ fn calculate<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
         deps: deps,
         local: local,
         memoized_hash: Mutex::new(None),
+        rustflags: try!(cx.rustflags_args(unit)),
     });
     cx.fingerprints.insert(*unit, fingerprint.clone());
     Ok(fingerprint)
@@ -425,6 +434,7 @@ pub fn prepare_build_cmd<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
         deps: Vec::new(),
         local: local,
         memoized_hash: Mutex::new(None),
+        rustflags: Vec::new(),
     };
     let compare = compare_old_fingerprint(&loc, &fingerprint);
     log_compare(unit, &compare);
diff --git a/src/cargo/ops/cargo_rustc/mod.rs b/src/cargo/ops/cargo_rustc/mod.rs
index dad110c208e..250870f4159 100644
--- a/src/cargo/ops/cargo_rustc/mod.rs
+++ b/src/cargo/ops/cargo_rustc/mod.rs
@@ -243,9 +243,9 @@ fn rustc(cx: &mut Context, unit: &Unit) -> CargoResult<Work> {
     let dep_info_loc = fingerprint::dep_info_loc(cx, unit);
     let cwd = cx.config.cwd().to_path_buf();
 
-    return Ok(Work::new(move |desc_tx| {
-        debug!("about to run: {}", rustc);
+    let rustflags = try!(cx.rustflags_args(unit));
 
+    return Ok(Work::new(move |desc_tx| {
         // Only at runtime have we discovered what the extra -L and -l
         // arguments are for native libraries, so we process those here. We
         // also need to be sure to add any -L paths for our plugins to the
@@ -267,6 +267,9 @@ fn rustc(cx: &mut Context, unit: &Unit) -> CargoResult<Work> {
             }
         }
 
+        // Add the arguments from RUSTFLAGS
+        rustc.args(&rustflags);
+
         desc_tx.send(rustc.to_string()).ok();
         try!(exec_engine.exec(rustc).chain_error(|| {
             human(format!("Could not compile `{}`.", name))
diff --git a/tests/test_cargo_compile_rustflags.rs b/tests/test_cargo_compile_rustflags.rs
new file mode 100644
index 00000000000..a95184cadfd
--- /dev/null
+++ b/tests/test_cargo_compile_rustflags.rs
@@ -0,0 +1,826 @@
+use std::io::Write;
+use std::fs::{self, File};
+use support::{project, execs, paths};
+use hamcrest::assert_that;
+
+fn setup() {
+}
+
+test!(env_rustflags_normal_source {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "")
+        .file("src/bin/a.rs", "fn main() {}")
+        .file("examples/b.rs", "fn main() {}")
+        .file("tests/c.rs", "#[test] fn f() { }")
+        .file("benches/d.rs", r#"
+            #![feature(test)]
+            extern crate test;
+            #[bench] fn run1(_ben: &mut test::Bencher) { }"#);
+    p.build();
+
+    // Use RUSTFLAGS to pass an argument that will generate an error
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus")
+                .arg("--lib"),
+                execs().with_status(101));
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus")
+                .arg("--bin=a"),
+                execs().with_status(101));
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus")
+                .arg("--example=b"),
+                execs().with_status(101));
+    assert_that(p.cargo("test").env("RUSTFLAGS", "-Z bogus"),
+                execs().with_status(101));
+    assert_that(p.cargo("bench").env("RUSTFLAGS", "-Z bogus"),
+                execs().with_status(101));
+});
+
+test!(env_rustflags_build_script {
+    // RUSTFLAGS should be passed to rustc for build scripts
+    // when --target is not specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+            #[cfg(not(foo))]
+            fn main() { }
+        "#);
+    p.build();
+
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_build_script_dep {
+    // RUSTFLAGS should be passed to rustc for build scripts
+    // when --target is not specified.
+    // In this test if --cfg foo is not passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+
+            [build-dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+        "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(not(foo))]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    assert_that(foo.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_plugin {
+    // RUSTFLAGS should be passed to rustc for plugins
+    // when --target is not specified.
+    // In this test if --cfg foo is not passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+        "#)
+        .file("src/lib.rs", r#"
+            fn main() { }
+            #[cfg(not(foo))]
+            fn main() { }
+        "#);
+    p.build();
+
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_plugin_dep {
+    // RUSTFLAGS should be passed to rustc for plugins
+    // when --target is not specified.
+    // In this test if --cfg foo is not passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+
+            [dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn foo() { }
+        "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+
+            [lib]
+            name = "bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(not(foo))]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    assert_that(foo.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_normal_source_with_target {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "")
+        .file("src/bin/a.rs", "fn main() {}")
+        .file("examples/b.rs", "fn main() {}")
+        .file("tests/c.rs", "#[test] fn f() { }")
+        .file("benches/d.rs", r#"
+            #![feature(test)]
+            extern crate test;
+            #[bench] fn run1(_ben: &mut test::Bencher) { }"#);
+    p.build();
+
+    let ref host = ::rustc_host();
+
+    // Use RUSTFLAGS to pass an argument that will generate an error
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus")
+                .arg("--lib").arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus")
+                .arg("--bin=a").arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus")
+                .arg("--example=b").arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("test").env("RUSTFLAGS", "-Z bogus")
+                .arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("bench").env("RUSTFLAGS", "-Z bogus")
+                .arg("--target").arg(host),
+                execs().with_status(101));
+});
+
+test!(env_rustflags_build_script_with_target {
+    // RUSTFLAGS should not be passed to rustc for build scripts
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+            #[cfg(foo)]
+            fn main() { }
+        "#);
+    p.build();
+
+    let host = ::rustc_host();
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_build_script_dep_with_target {
+    // RUSTFLAGS should not be passed to rustc for build scripts
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+
+            [build-dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+        "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(foo)]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    let host = ::rustc_host();
+    assert_that(foo.cargo("build").env("RUSTFLAGS", "--cfg foo")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_plugin_with_target {
+    // RUSTFLAGS should not be passed to rustc for plugins
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+        "#)
+        .file("src/lib.rs", r#"
+            fn main() { }
+            #[cfg(foo)]
+            fn main() { }
+        "#);
+    p.build();
+
+    let host = ::rustc_host();
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_plugin_dep_with_target {
+    // RUSTFLAGS should not be passed to rustc for plugins
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+
+            [dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn foo() { }
+        "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+
+            [lib]
+            name = "bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(foo)]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    let host = ::rustc_host();
+    assert_that(foo.cargo("build").env("RUSTFLAGS", "--cfg foo")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(env_rustflags_recompile {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "");
+    p.build();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(0));
+    // Setting RUSTFLAGS forces a recompile
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus"),
+                execs().with_status(101));
+});
+
+test!(env_rustflags_recompile2 {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "");
+    p.build();
+
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+    // Setting RUSTFLAGS forces a recompile
+    assert_that(p.cargo("build").env("RUSTFLAGS", "-Z bogus"),
+                execs().with_status(101));
+});
+
+test!(env_rustflags_no_recompile {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "");
+    p.build();
+
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_stdout("").with_status(0));
+});
+
+test!(build_rustflags_normal_source {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "")
+        .file("src/bin/a.rs", "fn main() {}")
+        .file("examples/b.rs", "fn main() {}")
+        .file("tests/c.rs", "#[test] fn f() { }")
+        .file("benches/d.rs", r#"
+            #![feature(test)]
+            extern crate test;
+            #[bench] fn run1(_ben: &mut test::Bencher) { }"#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["-Z", "bogus"]
+            "#);
+    p.build();
+
+    assert_that(p.cargo("build")
+                .arg("--lib"),
+                execs().with_status(101));
+    assert_that(p.cargo("build")
+                .arg("--bin=a"),
+                execs().with_status(101));
+    assert_that(p.cargo("build")
+                .arg("--example=b"),
+                execs().with_status(101));
+    assert_that(p.cargo("test"),
+                execs().with_status(101));
+    assert_that(p.cargo("bench"),
+                execs().with_status(101));
+});
+
+test!(build_rustflags_build_script {
+    // RUSTFLAGS should be passed to rustc for build scripts
+    // when --target is not specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+            #[cfg(not(foo))]
+            fn main() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    p.build();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_build_script_dep {
+    // RUSTFLAGS should be passed to rustc for build scripts
+    // when --target is not specified.
+    // In this test if --cfg foo is not passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+
+            [build-dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(not(foo))]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    assert_that(foo.cargo("build"),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_plugin {
+    // RUSTFLAGS should be passed to rustc for plugins
+    // when --target is not specified.
+    // In this test if --cfg foo is not passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+        "#)
+        .file("src/lib.rs", r#"
+            fn main() { }
+            #[cfg(not(foo))]
+            fn main() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    p.build();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_plugin_dep {
+    // RUSTFLAGS should be passed to rustc for plugins
+    // when --target is not specified.
+    // In this test if --cfg foo is not passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+
+            [dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn foo() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+
+            [lib]
+            name = "bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(not(foo))]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    assert_that(foo.cargo("build"),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_normal_source_with_target {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "")
+        .file("src/bin/a.rs", "fn main() {}")
+        .file("examples/b.rs", "fn main() {}")
+        .file("tests/c.rs", "#[test] fn f() { }")
+        .file("benches/d.rs", r#"
+            #![feature(test)]
+            extern crate test;
+            #[bench] fn run1(_ben: &mut test::Bencher) { }"#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["-Z", "bogus"]
+            "#);
+    p.build();
+
+    let ref host = ::rustc_host();
+
+    // Use RUSTFLAGS to pass an argument that will generate an error
+    assert_that(p.cargo("build")
+                .arg("--lib").arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("build")
+                .arg("--bin=a").arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("build")
+                .arg("--example=b").arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("test")
+                .arg("--target").arg(host),
+                execs().with_status(101));
+    assert_that(p.cargo("bench")
+                .arg("--target").arg(host),
+                execs().with_status(101));
+});
+
+test!(build_rustflags_build_script_with_target {
+    // RUSTFLAGS should not be passed to rustc for build scripts
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+            #[cfg(foo)]
+            fn main() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    p.build();
+
+    let host = ::rustc_host();
+    assert_that(p.cargo("build")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_build_script_dep_with_target {
+    // RUSTFLAGS should not be passed to rustc for build scripts
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+
+            [build-dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", "")
+        .file("build.rs", r#"
+            fn main() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(foo)]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    let host = ::rustc_host();
+    assert_that(foo.cargo("build")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_plugin_with_target {
+    // RUSTFLAGS should not be passed to rustc for plugins
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+        "#)
+        .file("src/lib.rs", r#"
+            fn main() { }
+            #[cfg(foo)]
+            fn main() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    p.build();
+
+    let host = ::rustc_host();
+    assert_that(p.cargo("build")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_plugin_dep_with_target {
+    // RUSTFLAGS should not be passed to rustc for plugins
+    // when --target is specified.
+    // In this test if --cfg foo is passed the build will fail.
+    let foo = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [lib]
+            name = "foo"
+            plugin = true
+
+            [dependencies.bar]
+            path = "../bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn foo() { }
+        "#)
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    let bar = project("bar")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "bar"
+            version = "0.0.1"
+
+            [lib]
+            name = "bar"
+        "#)
+        .file("src/lib.rs", r#"
+            fn bar() { }
+            #[cfg(foo)]
+            fn bar() { }
+        "#);
+    foo.build();
+    bar.build();
+
+    let host = ::rustc_host();
+    assert_that(foo.cargo("build")
+                .arg("--target").arg(host),
+                execs().with_status(0));
+});
+
+test!(build_rustflags_recompile {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "");
+    p.build();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(0));
+
+    // Setting RUSTFLAGS forces a recompile
+    let config = r#"
+        [build]
+        rustflags = ["-Z", "bogus"]
+        "#;
+    let config_file = paths::root().join("foo/.cargo/config");
+    fs::create_dir_all(config_file.parent().unwrap()).unwrap();
+    let mut config_file = File::create(config_file).unwrap();
+    config_file.write_all(config.as_bytes()).unwrap();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(101));
+});
+
+test!(build_rustflags_recompile2 {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "");
+    p.build();
+
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+
+    // Setting RUSTFLAGS forces a recompile
+    let config = r#"
+        [build]
+        rustflags = ["-Z", "bogus"]
+        "#;
+    let config_file = paths::root().join("foo/.cargo/config");
+    fs::create_dir_all(config_file.parent().unwrap()).unwrap();
+    let mut config_file = File::create(config_file).unwrap();
+    config_file.write_all(config.as_bytes()).unwrap();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(101));
+});
+
+test!(build_rustflags_no_recompile {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+        "#)
+        .file("src/lib.rs", "")
+        .file(".cargo/config", r#"
+            [build]
+            rustflags = ["--cfg", "foo"]
+            "#);
+    p.build();
+
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_status(0));
+    assert_that(p.cargo("build").env("RUSTFLAGS", "--cfg foo"),
+                execs().with_stdout("").with_status(0));
+});
diff --git a/tests/tests.rs b/tests/tests.rs
index 6b252a3e2e7..c163e1aea25 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -45,6 +45,7 @@ mod test_cargo_compile_custom_build;
 mod test_cargo_compile_git_deps;
 mod test_cargo_compile_path_deps;
 mod test_cargo_compile_plugins;
+mod test_cargo_compile_rustflags;
 mod test_cargo_cross_compile;
 mod test_cargo_doc;
 mod test_cargo_features;