diff --git a/dom/events/EventListenerManager.cpp b/dom/events/EventListenerManager.cpp
index eae7ed4eedc..c1833cd3ac7 100644
--- a/dom/events/EventListenerManager.cpp
+++ b/dom/events/EventListenerManager.cpp
@@ -300,7 +300,7 @@ EventListenerManager::AddEventListenerInternal(
       window->SetHasPaintEventListeners();
     }
   } else if (aEventMessage >= eLegacyMutationEventFirst &&
-             aEventMessage <= NS_MUTATION_END) {
+             aEventMessage <= eLegacyMutationEventLast) {
     // For mutation listeners, we need to update the global bit on the DOM window.
     // Otherwise we won't actually fire the mutation event.
     mMayHaveMutationListeners = true;
@@ -1227,7 +1227,7 @@ EventListenerManager::HasMutationListeners()
     for (uint32_t i = 0; i < count; ++i) {
       Listener* listener = &mListeners.ElementAt(i);
       if (listener->mEventMessage >= eLegacyMutationEventFirst &&
-          listener->mEventMessage <= NS_MUTATION_END) {
+          listener->mEventMessage <= eLegacyMutationEventLast) {
         return true;
       }
     }
@@ -1245,7 +1245,7 @@ EventListenerManager::MutationListenerBits()
     for (uint32_t i = 0; i < count; ++i) {
       Listener* listener = &mListeners.ElementAt(i);
       if (listener->mEventMessage >= eLegacyMutationEventFirst &&
-          listener->mEventMessage <= NS_MUTATION_END) {
+          listener->mEventMessage <= eLegacyMutationEventLast) {
         if (listener->mEventMessage == eLegacySubtreeModified) {
           return kAllMutationBits;
         }
diff --git a/widget/EventMessageList.h b/widget/EventMessageList.h
index 9da1d667678..67a2654a5c0 100644
--- a/widget/EventMessageList.h
+++ b/widget/EventMessageList.h
@@ -140,7 +140,7 @@ NS_EVENT_MESSAGE(eLegacyNodeRemovedFromDocument,  eLegacyMutationEventFirst + 3)
 NS_EVENT_MESSAGE(eLegacyNodeInsertedIntoDocument, eLegacyMutationEventFirst + 4)
 NS_EVENT_MESSAGE(eLegacyAttrModified,             eLegacyMutationEventFirst + 5)
 NS_EVENT_MESSAGE(eLegacyCharacterDataModified,    eLegacyMutationEventFirst + 6)
-NS_EVENT_MESSAGE(NS_MUTATION_END,                 eLegacyCharacterDataModified)
+NS_EVENT_MESSAGE(eLegacyMutationEventLast,        eLegacyCharacterDataModified)
 
 NS_EVENT_MESSAGE(NS_USER_DEFINED_EVENT, 2000)