diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 4b71e199d27..32640f8e946 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30031,6 +30031,8 @@ build_deduction_guide (tree type, tree ctor, tree outer_args, tsubst_flags_t com
 	     references to members of an unknown specialization.  */
 	  cp_evaluated ev;
 	  fparms = tsubst_arg_types (fparms, targs, NULL_TREE, complain, ctor);
+	 if (fparms == error_mark_node)
+	   ok = false;
 	  fargs = tsubst (fargs, targs, complain, ctor);
 	  if (ci)
 	    {
diff --git a/gcc/testsuite/g++.dg/parse/error66.C b/gcc/testsuite/g++.dg/parse/error66.C
new file mode 100644
index 00000000000..82f4b8b8a53
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/error66.C
@@ -0,0 +1,6 @@
+// PR c++/105760
+// { dg-do compile { target c++17 } }
+
+template<class... Ts, class> // { dg-error "must be at the end of the template parameter list" }
+struct A { A(Ts...); };
+A a;