diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
index 522b7c06a29..5254ac028d1 100644
--- a/gcc/cp/reflect.cc
+++ b/gcc/cp/reflect.cc
@@ -8086,6 +8086,14 @@ consteval_only_p (tree t)
   if (!t)
     return false;
 
+  if (TREE_CODE (t) == TREE_VEC)
+    {
+      for (tree arg : tree_vec_range (t))
+	if (arg && consteval_only_p (arg))
+	  return true;
+      return false;
+    }
+
   /* We need the complete type otherwise we'd have no fields for class
      templates and thus come up with zilch for things like
        template<typename T>
diff --git a/gcc/testsuite/g++.dg/reflect/pr124227.C b/gcc/testsuite/g++.dg/reflect/pr124227.C
new file mode 100644
index 00000000000..09e14043567
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/pr124227.C
@@ -0,0 +1,15 @@
+// PR c++/124227
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection -fopenmp" }
+// { dg-require-effective-target fopenmp }
+
+using b = float;
+template <typename> class c {};
+#pragma omp declare reduction(d : c<float> : omp_in)
+auto e = [] {
+c<b> acc;
+#pragma omp parallel reduction(d : acc)
+{
+}
+};
+