diff --git a/content/events/src/nsEventStateManager.cpp b/content/events/src/nsEventStateManager.cpp
index 28cd2d73bea3..756deeba6b36 100644
--- a/content/events/src/nsEventStateManager.cpp
+++ b/content/events/src/nsEventStateManager.cpp
@@ -1270,8 +1270,7 @@ nsEventStateManager::PreHandleEvent(nsPresContext* aPresContext,
     break;
   case NS_SELECTION_SET:
     {
-      WidgetSelectionEvent *selectionEvent =
-          static_cast<WidgetSelectionEvent*>(aEvent);
+      WidgetSelectionEvent* selectionEvent = aEvent->AsSelectionEvent();
       if (IsTargetCrossProcess(selectionEvent)) {
         // Will not be handled locally, remote the event
         if (GetCrossProcessTarget()->SendSelectionEvent(*selectionEvent))
@@ -1279,7 +1278,7 @@ nsEventStateManager::PreHandleEvent(nsPresContext* aPresContext,
         break;
       }
       nsContentEventHandler handler(mPresContext);
-      handler.OnSelectionEvent(static_cast<WidgetSelectionEvent*>(aEvent));
+      handler.OnSelectionEvent(selectionEvent);
     }
     break;
   case NS_CONTENT_COMMAND_CUT:
diff --git a/widget/xpwidgets/PuppetWidget.cpp b/widget/xpwidgets/PuppetWidget.cpp
index 0fba3d319a43..fd283851cead 100644
--- a/widget/xpwidgets/PuppetWidget.cpp
+++ b/widget/xpwidgets/PuppetWidget.cpp
@@ -285,7 +285,7 @@ PuppetWidget::DispatchEvent(WidgetGUIEvent* event, nsEventStatus& aStatus)
       return NS_OK;
     break;
   case NS_SELECTION_EVENT:
-    mIMELastReceivedSeqno = static_cast<WidgetSelectionEvent*>(event)->seqno;
+    mIMELastReceivedSeqno = event->AsSelectionEvent()->seqno;
     if (mIMELastReceivedSeqno < mIMELastBlurSeqno)
       return NS_OK;
     break;