diff --git a/js/src/jit-test/tests/debug/Debugger-getNewestFrame-03.js b/js/src/jit-test/tests/debug/Debugger-getNewestFrame-03.js
new file mode 100644
index 00000000000..b5de250a1c3
--- /dev/null
+++ b/js/src/jit-test/tests/debug/Debugger-getNewestFrame-03.js
@@ -0,0 +1,9 @@
+// Debugger.prototype.getNewestFrame() ignores dummy frames.
+// See bug 678086.
+
+var g = newGlobal('new-compartment');
+g.f = function () { return dbg.getNewestFrame(); };
+var dbg = new Debugger;
+var gw = dbg.addDebuggee(g);
+var fw = gw.getOwnPropertyDescriptor("f").value;
+assertEq(fw.call().return, null);
diff --git a/js/src/vm/Debugger.cpp b/js/src/vm/Debugger.cpp
index f15a859df55..04b992fd8ac 100644
--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -2562,7 +2562,7 @@ DebuggerFrame_getOlder(JSContext *cx, uintN argc, Value *vp)
     THIS_FRAME(cx, argc, vp, "get this", args, thisobj, thisfp);
     Debugger *dbg = Debugger::fromChildJSObject(thisobj);
     for (StackFrame *fp = thisfp->prev(); fp; fp = fp->prev()) {
-        if (!fp->isDummyFrame() && dbg->observesFrame(fp))
+        if (dbg->observesFrame(fp))
             return dbg->getScriptFrame(cx, fp, vp);
     }
     args.rval().setNull();
diff --git a/js/src/vm/Debugger.h b/js/src/vm/Debugger.h
index 4a597a68be3..f897d9a258c 100644
--- a/js/src/vm/Debugger.h
+++ b/js/src/vm/Debugger.h
@@ -483,7 +483,7 @@ Debugger::observesGlobal(GlobalObject *global) const
 bool
 Debugger::observesFrame(StackFrame *fp) const
 {
-    return observesGlobal(&fp->scopeChain().global());
+    return !fp->isDummyFrame() && observesGlobal(&fp->scopeChain().global());
 }
 
 JSTrapStatus