diff --git a/include/fmt/format.h b/include/fmt/format.h
index 59dc223b3465..1f89b63ec269 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -312,7 +312,7 @@ template <typename It> class is_output_iterator {
   using type = decltype(test<It>(typename iterator_category<It>::type{}));
 
  public:
-  static const bool value = !std::is_const<remove_reference_t<type>>::value;
+  enum { value = !std::is_const<remove_reference_t<type>>::value };
 };
 
 // A workaround for std::string not having mutable data() until C++17.