diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testSubstring.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testSubstring.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7 @@
+function testSubstring() {
+    for (var i = 0; i < 5; ++i) {
+        actual = "".substring(5);
+    }
+    return actual;
+}
+assertEq(testSubstring(), "");