diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/regexp-sticky-undef-capture.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/regexp-sticky-undef-capture.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,8 @@
+var re = /abc(WHOO!)?def/y;
+var input = 'abcdefabcdefabcdef';
+var count = 0;
+while ((match = re.exec(input)) !== null) {
+    print(count++);
+    assertEq(match[0], 'abcdef');
+    assertEq(match[1], undefined);
+}