--- a/mfbt/LinkedList.h
+++ b/mfbt/LinkedList.h
@@ -249,16 +249,20 @@ template<typename T>
 class LinkedList
 {
   private:
     LinkedListElement<T> sentinel;
 
   public:
     LinkedList() : sentinel(LinkedListElement<T>::NODE_KIND_SENTINEL) { }
 
+    ~LinkedList() {
+      MOZ_ASSERT(isEmpty());
+    }
+
     /*
      * Add elem to the front of the list.
      */
     void insertFront(T* elem) {
       /* Bypass setNext()'s this->isInList() assertion. */
       sentinel.setNextUnsafe(elem);
     }