diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 07f75ea6659..6a73507d074 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -222,6 +222,14 @@
 # endif
 #endif
 
+#ifndef _GLIBCXX26_CONSTEXPR
+# if __cplusplus >= 202400L
+#  define _GLIBCXX26_CONSTEXPR constexpr
+# else
+#  define _GLIBCXX26_CONSTEXPR
+# endif
+#endif
+
 #ifndef _GLIBCXX17_INLINE
 # if __cplusplus >= 201703L
 #  define _GLIBCXX17_INLINE inline