diff --git a/dom/events/EventNameList.h b/dom/events/EventNameList.h
index e1e6dafafcae..340a6de1de7b 100644
--- a/dom/events/EventNameList.h
+++ b/dom/events/EventNameList.h
@@ -909,7 +909,7 @@ NON_IDL_EVENT(transitionend,
               EventNameType_None,
               eTransitionEventClass)
 NON_IDL_EVENT(animationstart,
-              NS_ANIMATION_START,
+              eAnimationStart,
               EventNameType_None,
               eAnimationEventClass)
 NON_IDL_EVENT(animationend,
diff --git a/layout/style/nsAnimationManager.cpp b/layout/style/nsAnimationManager.cpp
index 12e7644882ca..05026058881f 100644
--- a/layout/style/nsAnimationManager.cpp
+++ b/layout/style/nsAnimationManager.cpp
@@ -239,7 +239,7 @@ CSSAnimation::QueueEvents()
   EventMessage message;
 
   if (!wasActive && isActive) {
-    message = NS_ANIMATION_START;
+    message = eAnimationStart;
   } else if (wasActive && !isActive) {
     message = NS_ANIMATION_END;
   } else if (wasActive && isActive && !isSameIteration) {
@@ -251,7 +251,7 @@ CSSAnimation::QueueEvents()
       std::min(StickyTimeDuration(mEffect->InitialAdvance()),
                computedTiming.mActiveDuration);
     manager->QueueEvent(
-      AnimationEventInfo(owningElement, mAnimationName, NS_ANIMATION_START,
+      AnimationEventInfo(owningElement, mAnimationName, eAnimationStart,
                          elapsedTime, owningPseudoType));
     // Then have the shared code below append an 'animationend':
     message = NS_ANIMATION_END;
@@ -261,7 +261,7 @@ CSSAnimation::QueueEvents()
 
   StickyTimeDuration elapsedTime;
 
-  if (message == NS_ANIMATION_START ||
+  if (message == eAnimationStart ||
       message == NS_ANIMATION_ITERATION) {
     TimeDuration iterationStart = mEffect->Timing().mIterationDuration *
                                     computedTiming.mCurrentIteration;
diff --git a/widget/EventMessageList.h b/widget/EventMessageList.h
index 4d02a5fa4aa7..6c7d4cc2fc43 100644
--- a/widget/EventMessageList.h
+++ b/widget/EventMessageList.h
@@ -327,7 +327,7 @@ NS_EVENT_MESSAGE(NS_TRANSITION_EVENT_START, 4200)
 NS_EVENT_MESSAGE(NS_TRANSITION_END,     NS_TRANSITION_EVENT_START)
 
 NS_EVENT_MESSAGE(eAnimationEventFirst,   4250)
-NS_EVENT_MESSAGE(NS_ANIMATION_START,     eAnimationEventFirst)
+NS_EVENT_MESSAGE(eAnimationStart,        eAnimationEventFirst)
 NS_EVENT_MESSAGE(NS_ANIMATION_END,       eAnimationEventFirst + 1)
 NS_EVENT_MESSAGE(NS_ANIMATION_ITERATION, eAnimationEventFirst + 2)