diff --git a/dom/bindings/BindingDeclarations.h b/dom/bindings/BindingDeclarations.h
index 35089d4c48a1..582a20fb8abc 100644
--- a/dom/bindings/BindingDeclarations.h
+++ b/dom/bindings/BindingDeclarations.h
@@ -119,6 +119,11 @@ public:
     mImpl.emplace(aValue);
   }
 
+  bool operator==(const Optional_base<T, InternalType>& aOther) const
+  {
+    return mImpl == aOther.mImpl;
+  }
+
   template<typename T1, typename T2>
   explicit Optional_base(const T1& aValue1, const T2& aValue2)
   {