diff --git a/googletest/include/gtest/internal/gtest-internal.h b/googletest/include/gtest/internal/gtest-internal.h
index da3ebd2b..7901cd3b 100644
--- a/googletest/include/gtest/internal/gtest-internal.h
+++ b/googletest/include/gtest/internal/gtest-internal.h
@@ -1199,6 +1199,7 @@ public:
   const std::string& get() const { return value; }
 
 private:
+  AdditionalMessage& operator=(AdditionalMessage&&);
   std::string value;
 };