diff --git a/modules/plugin/base/src/nsPluginNativeWindowOS2.cpp b/modules/plugin/base/src/nsPluginNativeWindowOS2.cpp
index 901878bbe5b4..3c487b996d75 100644
--- a/modules/plugin/base/src/nsPluginNativeWindowOS2.cpp
+++ b/modules/plugin/base/src/nsPluginNativeWindowOS2.cpp
@@ -139,7 +139,8 @@ private:
 public:
   // locals
   PFNWP GetWindowProc();
-  PluginWindowEvent * GetPluginWindowEvent(HWND aWnd, ULONG aMsg, MPARAM mp1, MPARAM mp2);
+  already_AddRefed<nsIRunnable> GetPluginWindowEvent(HWND aWnd, ULONG aMsg,
+                                                     MPARAM mp1, MPARAM mp2);
 
 private:
   PFNWP mPluginWinProc;
@@ -271,7 +272,7 @@ NS_IMETHODIMP PluginWindowEvent::Run()
   return NS_OK;
 }
 
-PluginWindowEvent*
+already_AddRefed<nsIRunnable>
 nsPluginNativeWindowOS2::GetPluginWindowEvent(HWND aWnd, ULONG aMsg, MPARAM aMp1, MPARAM aMp2)
 {
   if (!mWeakRef) {
diff --git a/modules/plugin/base/src/nsPluginNativeWindowWin.cpp b/modules/plugin/base/src/nsPluginNativeWindowWin.cpp
index 763bbbc3863e..1c90754ae170 100644
--- a/modules/plugin/base/src/nsPluginNativeWindowWin.cpp
+++ b/modules/plugin/base/src/nsPluginNativeWindowWin.cpp
@@ -145,7 +145,9 @@ public:
   // locals
   WNDPROC GetPrevWindowProc();
   WNDPROC GetWindowProc();
-  PluginWindowEvent * GetPluginWindowEvent(HWND aWnd, UINT aMsg, WPARAM aWParam, LPARAM aLParam);
+  already_AddRefed<nsIRunnable> GetPluginWindowEvent(HWND aWnd, UINT aMsg,
+                                                     WPARAM aWParam,
+                                                     LPARAM aLParam);
 
 private:
   WNDPROC mPrevWinProc;
@@ -437,7 +439,7 @@ NS_IMETHODIMP PluginWindowEvent::Run()
   return NS_OK;
 }
 
-PluginWindowEvent*
+already_AddRefed<nsIRunnable>
 nsPluginNativeWindowWin::GetPluginWindowEvent(HWND aWnd, UINT aMsg, WPARAM aWParam, LPARAM aLParam)
 {
   if (!mWeakRef) {