--- a/widget/ContentEvents.h
+++ b/widget/ContentEvents.h
@@ -299,18 +299,18 @@ public:
     InternalAnimationEvent* result =
       new InternalAnimationEvent(false, mMessage);
     result->AssignAnimationEventData(*this, true);
     result->mFlags = mFlags;
     return result;
   }
 
   nsString mAnimationName;
+  nsString mPseudoElement;
   float mElapsedTime;
-  nsString mPseudoElement;
 
   void AssignAnimationEventData(const InternalAnimationEvent& aEvent,
                                 bool aCopyTargets)
   {
     AssignEventData(aEvent, aCopyTargets);
 
     mAnimationName = aEvent.mAnimationName;
     mElapsedTime = aEvent.mElapsedTime;