diff --git a/impl/Cargo.toml b/impl/Cargo.toml
index d84d8c48..3bd34f72 100644
--- a/impl/Cargo.toml
+++ b/impl/Cargo.toml
@@ -44,7 +44,7 @@ features = ["full"]
 rustdoc-args = ["--cfg", "docsrs"]
 
 [lints.rust]
-unexpected_cfgs = { level = "warn", check-cfg = ["cfg(ci)", "cfg(nightly)"] }
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(ci)"] }
 
 [features]
 default = []
diff --git a/impl/build.rs b/impl/build.rs
deleted file mode 100644
index dbd20bb6..00000000
--- a/impl/build.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-#[cfg(not(feature = "testing-helpers"))]
-fn detect_nightly() {}
-
-#[cfg(feature = "testing-helpers")]
-fn detect_nightly() {
-    use rustc_version::{version_meta, Channel};
-
-    if version_meta().unwrap().channel == Channel::Nightly {
-        println!("cargo:rustc-cfg=nightly");
-    }
-}
-
-fn main() {
-    detect_nightly();
-}
diff --git a/impl/doc/error.md b/impl/doc/error.md
index 2aace519..132287d6 100644
--- a/impl/doc/error.md
+++ b/impl/doc/error.md
@@ -57,11 +57,11 @@ Backtraces don't work though, because the `Backtrace` type is only available in
 ## Example usage
 
 ```rust
-# #![cfg_attr(nightly, feature(error_generic_member_access))]
+# #![rustversion::attr(nightly, feature(error_generic_member_access))]
 // Nightly requires enabling this feature:
 // #![feature(error_generic_member_access)]
-# #[cfg(not(nightly))] fn main() {}
-# #[cfg(nightly)] fn main() {
+# #[rustversion::not(nightly)] fn main() {}
+# #[rustversion::nightly] fn main() {
 # use core::error::{request_ref, request_value, Error as __};
 # use std::backtrace::Backtrace;
 #
diff --git a/tests/generics.rs b/tests/generics.rs
index 42c568a4..6f887188 100644
--- a/tests/generics.rs
+++ b/tests/generics.rs
@@ -38,7 +38,6 @@ struct WrappedDouble<T: Clone, U: Clone>(T, U);
 #[from(forward)]
 struct WrappedDouble2<T: Clone, U: Clone>(T, U);
 
-#[cfg(nightly)]
 #[derive(
     From,
     FromStr,