diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index 29c58ec13b15..411588c626a5 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -85,6 +85,8 @@ template <typename T, typename Char> class is_streamable {
   using result = decltype(test<T>(0));
 
  public:
+  is_streamable() = default;
+
   static const bool value = result::value;
 };