diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/Environment-setVariable-03.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/Environment-setVariable-03.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,16 @@
+// setVariable cannot create new global variables.
+// (Other kinds of environment are tested in Environment-variables.js.)
+
+load(libdir + "asserts.js");
+
+var g = newGlobal();
+var dbg = new Debugger(g);
+var hits = 0;
+dbg.onDebuggerStatement = function (frame) {
+    assertThrowsInstanceOf(function () { frame.environment.setVariable("x", 7); }, TypeError);
+    hits++;
+};
+g.eval("debugger");
+assertEq("x" in g, false);
+assertEq(hits, 1);
+