diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index a056ecefd1d..dc6f2f37f9b 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -28189,6 +28189,11 @@ placeholder_type_constraint_dependent_p (tree t)
   tree id = unpack_concept_check (t);
   tree args = TREE_OPERAND (id, 1);
   tree first = TREE_VEC_ELT (args, 0);
+  if (ARGUMENT_PACK_P (first))
+    {
+      args = expand_template_argument_pack (args);
+      first = TREE_VEC_ELT (args, 0);
+    }
   gcc_checking_assert (TREE_CODE (first) == WILDCARD_DECL
 		       || is_auto (first));
   for (int i = 1; i < TREE_VEC_LENGTH (args); ++i)
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder5.C b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder5.C
new file mode 100644
index 00000000000..eaea41a36eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder5.C
@@ -0,0 +1,32 @@
+// PR c++/99815
+// { dg-do compile { target c++20 } }
+
+template <class T, class U>
+struct is_same { static constexpr bool value = false; };
+
+template <class T>
+struct is_same<T, T> { static constexpr bool value = true; };
+
+template <class... Ts>
+concept C = is_same<Ts...>::value; // { dg-error "wrong number" }
+
+template <class... Ts> void f() {
+  C<Ts...> auto x = 0; // { dg-error "constraints" }
+}
+
+template void f<int>(); // { dg-bogus "" }
+template void f<char>(); // { dg-message "required from here" }
+template void f<>(); // { dg-message "required from here" }
+template void f<int, int>(); // { dg-message "required from here" }
+
+template <class... Ts> void g() {
+  C<Ts..., int> auto x = 0; // { dg-error "constraints" }
+}
+
+template void g<>(); // { dg-bogus "" }
+template void g<int>(); // { dg-message "required from here" }
+
+template <class> void h() {
+  C<char> auto x = 0; // { dg-error "constraints" }
+  C<int> auto y = 0;
+}