diff --git a/googletest/include/gtest/internal/gtest-internal.h b/googletest/include/gtest/internal/gtest-internal.h
index 08a9f9b..738e6c3 100644
--- a/googletest/include/gtest/internal/gtest-internal.h
+++ b/googletest/include/gtest/internal/gtest-internal.h
@@ -1325,8 +1325,8 @@
 namespace std {
 
 template <typename... Ts>
-struct tuple_size<testing::internal::FlatTuple<Ts...>>
-    : std::integral_constant<size_t, sizeof...(Ts)> {};
+class tuple_size<testing::internal::FlatTuple<Ts...>>
+    : public std::integral_constant<size_t, sizeof...(Ts)> {};
 
 }  // namespace std