--- a/xpcom/string/nsASCIIMask.h
+++ b/xpcom/string/nsASCIIMask.h
@@ -57,14 +57,14 @@ constexpr std::array<bool, 128> CreateAS
 {
   return {{ fun(Indices)... }};
 }
 } // namespace details
 
 template<typename F>
 constexpr std::array<bool, 128> CreateASCIIMask(F fun)
 {
-  return details::CreateASCIIMask(fun, std::make_index_sequence<128>::Type{});
+  return details::CreateASCIIMask(fun, std::make_index_sequence<128>);
 }
 
 } // namespace mozilla
 
 #endif // nsASCIIMask_h_