--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -2578,17 +2578,17 @@ GeckoDriver.prototype.quitApplication = 
     }
   } else {
     mode = eAttemptQuit;
   }
 
   try {
     this._server.acceptConnections = false;
     this.deleteSession();
-    resp.send();
+    Services.obs.addObserver(resp.send, "quit-application", false);
   } finally {
     Services.startup.quit(mode);
   }
 };
 
 GeckoDriver.prototype.installAddon = function (cmd, resp) {
   assert.firefox()