diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug572229.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug572229.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,12 @@
+// Don't crash
+
+function f(o, s) {
+    var k = s.substr(0, 1);
+    var c;
+    for (var i = 0; i < 10; ++i) {
+	c = k in o;
+    }
+    return c;
+}
+
+assertEq(f({ a: 66 }, 'abc'), true);