diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index e065ace5c55c64bc13e8c154dd0f6e8bf84578d4..68a056acf8b6014325b259258d298e4abc74b701 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -23895,11 +23895,6 @@ try_class_unification (tree tparms, tree targs, tree parm, tree arg,
     err = unify (tparms, targs, CLASSTYPE_TI_ARGS (parm),
 		 CLASSTYPE_TI_ARGS (arg), UNIFY_ALLOW_NONE, explain_p);
 
-  if (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (targs))
-    for (tree level : tree_vec_range (targs))
-      ggc_free (level);
-  ggc_free (targs);
-
   return err ? NULL_TREE : arg;
 }
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder13.C b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder13.C
new file mode 100644
index 0000000000000000000000000000000000000000..ac9f84524d31cf329251546edc927324aeff14db
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder13.C
@@ -0,0 +1,18 @@
+// PR c++/109556
+// { dg-do compile { target c++20 } }
+
+template<class T, auto N>
+concept C = (N != 0);
+
+template<auto N, auto M>
+struct A { };
+
+template<auto N, C<N> auto M>
+void f(A<N, M>);
+
+int main() {
+  f(A<1, 42>{});
+  f(A<2, 42>{});
+  f(A<1, 43>{});
+  f(A<2, 43>{});
+}