diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testNullIncrement.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testNullIncrement.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,14 @@
+function f() {
+    var n;
+    var k;
+    for (var i = 0; i < 18; ++i) {
+	n = null;
+	k = n++;
+	if (k) { }
+    }
+    return [k, n];
+}
+
+var [a, b] = f();
+assertEq(a, 0);
+assertEq(b, 1);