diff --git a/src/libcore/extfmt.rs b/src/libcore/extfmt.rs
index 04600a628a01..cd9ccff88d00 100644
--- a/src/libcore/extfmt.rs
+++ b/src/libcore/extfmt.rs
@@ -453,15 +453,6 @@ mod rt {
     }
 }
 
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn test_percent() {
-        let s = #fmt["ab%%cd"];
-        assert(s == "ab%cd");
-    }
-}
-
 // Local Variables:
 // mode: rust;
 // fill-column: 78;
diff --git a/src/test/run-pass/syntax-extension-fmt.rs b/src/test/run-pass/syntax-extension-fmt.rs
index c5a26bcaad20..3caeec912d9e 100644
--- a/src/test/run-pass/syntax-extension-fmt.rs
+++ b/src/test/run-pass/syntax-extension-fmt.rs
@@ -21,6 +21,7 @@ fn main() {
     part4();
     part5();
     part6();
+    percent();
 }
 
 fn part1() {
@@ -229,3 +230,8 @@ fn part6() {
     test(#fmt["%-+05d", 1], "+1   ");
     test(#fmt["%-+05d", -1], "-1   ");
 }
+
+fn percent() {
+    let s = #fmt["ab%%cd"];
+    assert(s == "ab%cd");
+}