diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 1391dc7a95371..a6146f9e5c910 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -74,7 +74,7 @@
 #![feature(const_alloc_layout)]
 #![feature(const_discriminant)]
 #![cfg_attr(bootstrap, feature(const_if_match))]
-#![feature(const_loop)]
+#![cfg_attr(bootstrap, feature(const_loop))]
 #![feature(const_checked_int_methods)]
 #![feature(const_euclidean_int_methods)]
 #![feature(const_overflowing_int_methods)]
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index d64105f3b99cc..cb6893166fd79 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -11,7 +11,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(box_syntax)]
 #![feature(const_fn)]
 #![cfg_attr(bootstrap, feature(const_if_match))]
-#![feature(const_loop)]
+#![cfg_attr(bootstrap, feature(const_loop))]
 #![feature(const_panic)]
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]