diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/Environment-setVariable-06.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/Environment-setVariable-06.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,9 @@
+// setVariable on an argument works as expected with non-strict 'arguments'.
+
+var g = newGlobal();
+g.eval("function f(a) { debugger; return arguments[0]; }");
+var dbg = new Debugger(g);
+dbg.onDebuggerStatement = function (frame) {
+    frame.environment.setVariable("a", 2);
+};
+assertEq(g.f(1), 2);