diff --git a/src/librustc_trans/common.rs b/src/librustc_trans/common.rs
index cab908c6621c4..22a501643280a 100644
--- a/src/librustc_trans/common.rs
+++ b/src/librustc_trans/common.rs
@@ -741,13 +741,14 @@ pub fn C_integral(t: Type, u: u64, sign_extend: bool) -> ValueRef {
     }
 }
 
-pub fn C_big_integral(t: Type, u: u128) -> ValueRef {
+pub fn C_big_integral(t: Type, u: u128, sign_extend: bool) -> ValueRef {
     if ::std::mem::size_of::<u128>() == 16 {
         unsafe {
             llvm::LLVMConstIntOfArbitraryPrecision(t.to_ref(), 2, &u as *const u128 as *const u64)
         }
     } else {
-        C_integral(t, u as u64, false)
+        // SNAP: remove after snapshot
+        C_integral(t, u as u64, sign_extend)
     }
 }
 
diff --git a/src/librustc_trans/mir/constant.rs b/src/librustc_trans/mir/constant.rs
index 3aa814e7b6a8e..8f2ab9be0806e 100644
--- a/src/librustc_trans/mir/constant.rs
+++ b/src/librustc_trans/mir/constant.rs
@@ -78,7 +78,7 @@ impl<'tcx> Const<'tcx> {
             ConstVal::Integral(I16(v)) => C_integral(Type::i16(ccx), v as u64, true),
             ConstVal::Integral(I32(v)) => C_integral(Type::i32(ccx), v as u64, true),
             ConstVal::Integral(I64(v)) => C_integral(Type::i64(ccx), v as u64, true),
-            ConstVal::Integral(I128(v)) => C_big_integral(Type::i128(ccx), v as u128),
+            ConstVal::Integral(I128(v)) => C_big_integral(Type::i128(ccx), v as u128, true),
             ConstVal::Integral(Isize(v)) => {
                 let i = v.as_i64(ccx.tcx().sess.target.int_type);
                 C_integral(Type::int(ccx), i as u64, true)
@@ -87,7 +87,7 @@ impl<'tcx> Const<'tcx> {
             ConstVal::Integral(U16(v)) => C_integral(Type::i16(ccx), v as u64, false),
             ConstVal::Integral(U32(v)) => C_integral(Type::i32(ccx), v as u64, false),
             ConstVal::Integral(U64(v)) => C_integral(Type::i64(ccx), v, false),
-            ConstVal::Integral(U128(v)) => C_big_integral(Type::i128(ccx), v),
+            ConstVal::Integral(U128(v)) => C_big_integral(Type::i128(ccx), v, false),
             ConstVal::Integral(Usize(v)) => {
                 let u = v.as_u64(ccx.tcx().sess.target.uint_type);
                 C_integral(Type::int(ccx), u, false)