--- a/gfx/layers/ipc/PAPZCTreeManager.ipdl
+++ b/gfx/layers/ipc/PAPZCTreeManager.ipdl
@@ -1,15 +1,16 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 include "mozilla/GfxMessageUtils.h";
 include "ipc/nsGUIEventIPC.h";
+include "mozilla/dom/TabMessageUtils.h"; // Needed for IPC::ParamTraits<nsEventStatus>.
 
 include protocol PCompositorBridge;
 
 using CSSRect from "Units.h";
 using LayoutDeviceCoord from "Units.h";
 using LayoutDeviceIntPoint from "Units.h";
 using mozilla::LayoutDevicePoint from "Units.h";
 using ScreenPoint from "Units.h";