From a9ea225cadc2ad0d0620ddd458310b24d2a1b4b8 Mon Sep 17 00:00:00 2001
From: Yat Ho <lagoho7@gmail.com>
Date: Sat, 17 Jan 2026 02:48:40 +0800
Subject: [PATCH] Fix C++20 concept detection (#4653)

---
 include/fmt/base.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/fmt/base.h b/include/fmt/base.h
index 3bd16fcf..37eb589e 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -2803,7 +2803,7 @@ template <typename T, typename Char = char>
 using is_formattable = bool_constant<!std::is_same<
     detail::mapped_t<conditional_t<std::is_void<T>::value, int*, T>, Char>,
     void>::value>;
-#ifdef __cpp_concepts
+#if defined(__cpp_concepts) && __cpp_concepts >= 201907L
 template <typename T, typename Char = char>
 concept formattable = is_formattable<remove_reference_t<T>, Char>::value;
 #endif