diff --git a/libstdc++-v3/include/c_global/cmath b/libstdc++-v3/include/c_global/cmath
index ca84f951400..5c568c70313 100644
--- a/libstdc++-v3/include/c_global/cmath
+++ b/libstdc++-v3/include/c_global/cmath
@@ -2880,8 +2880,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   constexpr _Float16
   nextafter(_Float16 __x, _Float16 __y)
   {
-    if (std::__is_constant_evaluated())
-      return __builtin_nextafterf16(__x, __y);
+#if __cpp_if_consteval >= 202106L
+    // Can't use if (std::__is_constant_evaluated()) here, as it
+    // doesn't guarantee optimizing the body away at -O0 and
+    // nothing defines nextafterf16.
+    if consteval { return __builtin_nextafterf16(__x, __y); }
+#endif
 #ifdef __INT16_TYPE__
     using __float16_int_type = __INT16_TYPE__;
 #else
@@ -3598,8 +3602,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   constexpr __gnu_cxx::__bfloat16_t
   nextafter(__gnu_cxx::__bfloat16_t __x, __gnu_cxx::__bfloat16_t __y)
   {
-    if (std::__is_constant_evaluated())
-      return __builtin_nextafterf16b(__x, __y);
+#if __cpp_if_consteval >= 202106L
+    // Can't use if (std::__is_constant_evaluated()) here, as it
+    // doesn't guarantee optimizing the body away at -O0 and
+    // nothing defines nextafterf16b.
+    if consteval { return __builtin_nextafterf16b(__x, __y); }
+#endif
 #ifdef __INT16_TYPE__
     using __bfloat16_int_type = __INT16_TYPE__;
 #else
diff --git a/libstdc++-v3/testsuite/26_numerics/headers/cmath/117321.cc b/libstdc++-v3/testsuite/26_numerics/headers/cmath/117321.cc
new file mode 100644
index 00000000000..18d108c6a3e
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/headers/cmath/117321.cc
@@ -0,0 +1,5 @@
+// { dg-do run { target c++23 } }
+// { dg-require-cmath "" }
+// { dg-additional-options "-O0" }
+
+#include "nextafter_c++23.cc"