diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug839420.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug839420.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+function f() {
+    var x = undefined;
+    try {
+	[1, 2, 3].map(x);
+	assertEq(0, 1);
+    } catch(e) {
+	assertEq(e.toString().contains("x is not"), true);
+    }
+
+    try {
+	[1, 2, 3].filter(x, 1, 2);
+	assertEq(0, 1);
+    } catch(e) {
+	assertEq(e.toString().contains("x is not"), true);
+    }
+}
+f();