-#![feature(allow_internal_unstable)]
-#![feature(extend_one)]
-#![feature(min_specialization)]
-#![feature(new_uninit)]
-#![feature(step_trait)]
-#![feature(stmt_expr_attributes)]
-#![feature(test)]
+#![cfg_attr(feature = "nightly", feature(allow_internal_unstable))]
+#![cfg_attr(feature = "nightly", feature(extend_one))]
+#![cfg_attr(feature = "nightly", feature(min_specialization))]
+#![cfg_attr(feature = "nightly", feature(new_uninit))]
+#![cfg_attr(feature = "nightly", feature(step_trait))]
+#![cfg_attr(feature = "nightly", feature(stmt_expr_attributes))]
+#![cfg_attr(feature = "nightly", feature(test))]