--- a/mfbt/LinkedList.h
+++ b/mfbt/LinkedList.h
@@ -553,18 +553,20 @@ public:
    * Measures the memory consumption of the list excluding |this|.  Note that
    * it only measures the list elements themselves.  If the list elements
    * contain pointers to other memory blocks, those blocks must be measured
    * separately during a subsequent iteration over the list.
    */
   size_t sizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
   {
     size_t n = 0;
-    for (ConstRawType t = getFirst(); t; t = t->getNext()) {
+    ConstRawType t = getFirst();
+    while (t) {
       n += aMallocSizeOf(t);
+      t = static_cast<const LinkedListElement<T>*>(t)->getNext();
     }
     return n;
   }
 
   /*
    * Like sizeOfExcludingThis(), but measures |this| as well.
    */
   size_t sizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const