diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index 96484b53..3ea41c8c 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -155,6 +155,8 @@ template <typename T>
 struct has_mutable_begin_end<
     T, void_t<decltype(detail::range_begin(std::declval<T>())),
               decltype(detail::range_end(std::declval<T>())),
+              // the extra int here is because older versions of MSVC don't
+              // SFINAE properly unless there are distinct types
               int>>
     : std::true_type {};