diff --git a/widget/EventMessageList.h b/widget/EventMessageList.h
index 8b9b97341052..4a169a4e3785 100644
--- a/widget/EventMessageList.h
+++ b/widget/EventMessageList.h
@@ -128,9 +128,9 @@ NS_EVENT_MESSAGE(eLegacyMouseScrollEventFirst, 1600)
 NS_EVENT_MESSAGE(eLegacyMouseLineOrPageScroll, eLegacyMouseScrollEventFirst)
 NS_EVENT_MESSAGE(eLegacyMousePixelScroll,      eLegacyMouseScrollEventFirst + 1)
 
-NS_EVENT_MESSAGE(NS_SCROLLPORT_START,     1700)
-NS_EVENT_MESSAGE(eScrollPortUnderflow,  NS_SCROLLPORT_START)
-NS_EVENT_MESSAGE(eScrollPortOverflow,   NS_SCROLLPORT_START + 1)
+NS_EVENT_MESSAGE(eScrollPortEventFirst, 1700)
+NS_EVENT_MESSAGE(eScrollPortUnderflow,  eScrollPortEventFirst)
+NS_EVENT_MESSAGE(eScrollPortOverflow,   eScrollPortEventFirst + 1)
 
 NS_EVENT_MESSAGE(eLegacyMutationEventFirst,       1800)
 NS_EVENT_MESSAGE(eLegacySubtreeModified,          eLegacyMutationEventFirst)