diff --git a/include/spdlog/common.h b/include/spdlog/common.h
index fdeae6a0..b7297d3e 100644
--- a/include/spdlog/common.h
+++ b/include/spdlog/common.h
@@ -162,6 +162,7 @@ struct format_string_wrapper
     {}
 #else
     template <typename S>
+    requires std::is_convertible_v<S, T>
     SPDLOG_CONSTEXPR format_string_wrapper(S fmtstr, details::source_location loc = details::source_location::current())
         : fmt_{fmtstr}
         , loc_{loc}