diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/Frame-onStep-03.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/Frame-onStep-03.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,28 @@
+// Setting onStep does not affect later calls to the same function.
+// (onStep is per-frame, not per-function.)
+
+var g = newGlobal();
+g.a = 1;
+g.eval("function f(a) {\n" +
+       "    var x = 2 * a;\n" +
+       "    return x * x;\n" +
+       "}\n");
+
+var dbg = Debugger(g);
+var log = '';
+dbg.onEnterFrame = function (frame) {
+    log += '+';
+    frame.onStep = function () {
+        if (log.charAt(log.length - 1) != 's')
+            log += 's';
+    };
+};
+
+g.f(1);
+log += '|';
+g.f(2);
+log += '|';
+dbg.onEnterFrame = undefined;
+g.f(3);
+
+assertEq(log, '+s|+s|');