diff --git a/netwerk/cache/nsCacheEntry.cpp b/netwerk/cache/nsCacheEntry.cpp
index abf58c64181..a2507b10621 100644
--- a/netwerk/cache/nsCacheEntry.cpp
+++ b/netwerk/cache/nsCacheEntry.cpp
@@ -436,6 +436,9 @@ nsCacheEntryHashTable::AddEntry( nsCacheEntry *cacheEntry)
     if (!cacheEntry)   return NS_ERROR_NULL_POINTER;
 
     hashEntry = table.Add(&(cacheEntry->mKey), fallible);
+
+    if (!hashEntry)
+        return NS_ERROR_FAILURE;
 #ifndef DEBUG_dougt
     NS_ASSERTION(((nsCacheEntryHashTableEntry *)hashEntry)->cacheEntry == 0,
                  "### nsCacheEntryHashTable::AddEntry - entry already used");