diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 72bbc4a96c5..1d5e12b0d41 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -683,7 +683,7 @@ pub fn std_macros() -> @str {
         ($cond:expr) => {
             if !$cond {
                 ::std::sys::FailWithCause::fail_with(
-                    ~\"assertion failed: \" + stringify!($cond), file!(), line!())
+                    \"assertion failed: \" + stringify!($cond), file!(), line!())
             }
         };
         ($cond:expr, $msg:expr) => {