--- a/ipc/mscom/WeakRef.h
+++ b/ipc/mscom/WeakRef.h
@@ -100,30 +100,32 @@ protected:
 
 private:
   RefPtr<detail::SharedRef> mSharedRef;
   ULONG                     mRefCnt;
   Flags                     mFlags;
   CRITICAL_SECTION          mCSForQI;
 };
 
-class WeakRef : public IWeakReference
+class WeakRef final : public IWeakReference
 {
 public:
   // IUnknown
   STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override;
   STDMETHODIMP_(ULONG) AddRef() override;
   STDMETHODIMP_(ULONG) Release() override;
 
   // IWeakReference
   STDMETHODIMP Resolve(REFIID aIid, void** aOutStrongReference) override;
 
   explicit WeakRef(RefPtr<detail::SharedRef>& aSharedRef);
 
 private:
+  ~WeakRef() = default;
+
   Atomic<ULONG>             mRefCnt;
   RefPtr<detail::SharedRef> mSharedRef;
 };
 
 } // namespace mscom
 } // namespace mozilla
 
 #endif // mozilla_mscom_WeakRef_h