diff --git a/dom/base/EventSource.cpp b/dom/base/EventSource.cpp
index 02fe1d840d4c..57a4d4775531 100644
--- a/dom/base/EventSource.cpp
+++ b/dom/base/EventSource.cpp
@@ -1454,11 +1454,7 @@ EventSourceImpl::DispatchCurrentMessageEvent()
     message->mLastEventID.Assign(mLastEventID);
   }
 
-  size_t sizeBefore = mMessagesToDispatch.GetSize();
   mMessagesToDispatch.Push(message.release());
-  NS_ENSURE_TRUE(mMessagesToDispatch.GetSize() == sizeBefore + 1,
-                 NS_ERROR_OUT_OF_MEMORY);
-
 
   if (!mGoingToDispatchAllMessages) {
     nsCOMPtr<nsIRunnable> event =