diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index d5190b65863c..c49292481c3f 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -72,6 +72,7 @@
 #![feature(cfg_target_has_atomic)]
 #![feature(concat_idents)]
 #![feature(const_fn)]
+#![feature(convert_id)]
 #![feature(custom_attribute)]
 #![feature(fundamental)]
 #![feature(i128_type)]
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index bb38fc550917..880b46fa5071 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -256,6 +256,7 @@
 #![feature(collections_range)]
 #![feature(compiler_builtins_lib)]
 #![feature(const_fn)]
+#![feature(convert_id)]
 #![feature(core_float)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]