--- a/layout/printing/nsPagePrintTimer.cpp
+++ b/layout/printing/nsPagePrintTimer.cpp
@@ -3,17 +3,17 @@
  * 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 "nsPagePrintTimer.h"
 #include "nsIContentViewer.h"
 #include "nsIServiceManager.h"
 #include "nsPrintEngine.h"
 
-NS_IMPL_ISUPPORTS1(nsPagePrintTimer, nsITimerCallback)
+NS_IMPL_ISUPPORTS_INHERITED1(nsPagePrintTimer, nsRunnable, nsITimerCallback)
 
 nsPagePrintTimer::~nsPagePrintTimer()
 {
   // "Destroy" the document viewer; this normally doesn't actually
   // destroy it because of the IncrementDestroyRefCount call below
   // XXX This is messy; the document viewer should use a single approach
   // to keep itself alive during printing
   nsCOMPtr<nsIContentViewer> cv(do_QueryInterface(mDocViewerPrint));

--- a/layout/printing/nsPagePrintTimer.h
+++ b/layout/printing/nsPagePrintTimer.h
@@ -13,18 +13,18 @@
 #include "mozilla/Attributes.h"
 #include "nsThreadUtils.h"
 
 class nsPrintEngine;
 
 //---------------------------------------------------
 //-- Page Timer Class
 //---------------------------------------------------
-class nsPagePrintTimer MOZ_FINAL : public nsITimerCallback,
-                                   public nsRunnable
+class nsPagePrintTimer MOZ_FINAL : public nsRunnable,
+                                   public nsITimerCallback
 {
 public:
 
   NS_DECL_ISUPPORTS
 
   nsPagePrintTimer(nsPrintEngine* aPrintEngine,
                    nsIDocumentViewerPrint* aDocViewerPrint,
                    uint32_t aDelay)