diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testBug784639.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testBug784639.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+evalcx("\
+  Object.defineProperty(this, \"a\", {});\
+  f = (function(j) {\
+	  a = Proxy\
+  });\
+  Object.defineProperty(this, \"g\", {\
+	  get: function() {\
+		  return ({\
+			  r: function() {},\
+			  t: function() {}\
+		  })\
+	  }\
+  });\
+  for (p in g) {\
+	  f(1)\
+  }\
+", newGlobal())