diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/onExceptionUnwind-06.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/onExceptionUnwind-06.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,14 @@
+// |jit-test| debug
+// onExceptionUnwind assigning to argv[1] does not affect the thrown exception.
+
+var g = newGlobal();
+g.parent = this;
+g.eval("function f(frame, exc) { f2 = function () { return exc; }; exc = 123; }");
+g.eval("new Debugger(parent).onExceptionUnwind = f;");
+
+var obj = new Error("oops");
+try {
+    throw obj;
+} catch (exc) {
+    assertEq(exc, obj);
+}