diff --git a/accessible/src/base/NotificationController.cpp b/accessible/src/base/NotificationController.cpp
index a51a2324b99..f90f891613c 100644
--- a/accessible/src/base/NotificationController.cpp
+++ b/accessible/src/base/NotificationController.cpp
@@ -592,8 +592,8 @@ NotificationController::CoalesceSelChangeEvents(AccSelChangeEvent* aTailEvent,
     if (aThisEvent->mPackedEvent) {
       aThisEvent->mPackedEvent->mEventType =
         aThisEvent->mPackedEvent->mSelChangeType == AccSelChangeEvent::eSelectionAdd ?
-          nsIAccessibleEvent::EVENT_SELECTION_ADD :
-          nsIAccessibleEvent::EVENT_SELECTION_REMOVE;
+          static_cast<PRUint32>(nsIAccessibleEvent::EVENT_SELECTION_ADD) :
+          static_cast<PRUint32>(nsIAccessibleEvent::EVENT_SELECTION_REMOVE);
 
       aThisEvent->mPackedEvent->mEventRule =
         AccEvent::eCoalesceSelectionChange;
@@ -603,8 +603,8 @@ NotificationController::CoalesceSelChangeEvents(AccSelChangeEvent* aTailEvent,
 
     aThisEvent->mEventType =
       aThisEvent->mSelChangeType == AccSelChangeEvent::eSelectionAdd ?
-        nsIAccessibleEvent::EVENT_SELECTION_ADD :
-        nsIAccessibleEvent::EVENT_SELECTION_REMOVE;
+        static_cast<PRUint32>(nsIAccessibleEvent::EVENT_SELECTION_ADD) :
+        static_cast<PRUint32>(nsIAccessibleEvent::EVENT_SELECTION_REMOVE);
 
     return;
   }