diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index a99372f178b..e92e340b86c 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -67,6 +67,7 @@ use core::option::Option::{self, Some, None};
 use core::result::Result;
 use core::slice::AsSlice;
 use core::str as core_str;
+#[cfg(stage0)]
 use unicode::char::CharExt;
 use unicode::str::{UnicodeStr, Utf16Encoder};