diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0d061adc2ed..beabcc4b027 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -23584,13 +23584,21 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	  /* We haven't deduced the type of this parameter yet.  */
 	  if (cxx_dialect >= cxx17
 	      /* We deduce from array bounds in try_array_deduction.  */
-	      && !(strict & UNIFY_ALLOW_INTEGER))
+	      && !(strict & UNIFY_ALLOW_INTEGER)
+	      && TEMPLATE_PARM_LEVEL (parm) <= TMPL_ARGS_DEPTH (targs))
 	    {
 	      /* Deduce it from the non-type argument.  */
 	      tree atype = TREE_TYPE (arg);
 	      RECUR_AND_CHECK_FAILURE (tparms, targs,
 				       tparm, atype,
 				       UNIFY_ALLOW_NONE, explain_p);
+	      /* Now check whether the type of this parameter is still
+		 dependent, and give up if so.  */
+	      ++processing_template_decl;
+	      tparm = tsubst (tparm, targs, tf_none, NULL_TREE);
+	      --processing_template_decl;
+	      if (uses_template_parms (tparm))
+		return unify_success (explain_p);
 	    }
 	  else
 	    /* Try again later.  */
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto17.C b/gcc/testsuite/g++.dg/cpp1z/nontype-auto17.C
new file mode 100644
index 00000000000..509eb0e98e3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto17.C
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++11 } }
+
+template <int> struct K { };
+
+template <class T = void, typename T::type M> int f(K<M>); // { dg-error "void" }
+int a = f(K<42>{}); // { dg-error "no match" }
+
+struct S { using type = void; };
+template <class T = S, typename T::type M> int g(K<M>); // { dg-message "deduction" }
+int b = g(K<42>{}); // { dg-error "no match" }
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto18.C b/gcc/testsuite/g++.dg/cpp1z/nontype-auto18.C
new file mode 100644
index 00000000000..936c841ce31
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto18.C
@@ -0,0 +1,7 @@
+// { dg-do compile { target c++11 } }
+
+template <int> struct K { };
+
+struct S { using type = int; };
+template <class T = S, typename T::type M> int g(K<M>);
+int a = g(K<42>{});
diff --git a/gcc/testsuite/g++.dg/template/partial5.C b/gcc/testsuite/g++.dg/template/partial5.C
index a56229770f4..40d8c45b087 100644
--- a/gcc/testsuite/g++.dg/template/partial5.C
+++ b/gcc/testsuite/g++.dg/template/partial5.C
@@ -14,7 +14,7 @@ template<typename T, typename T::foo V>
 struct Y { };
 
 template<typename T, typename U, U v>
-struct Y<T, v> { }; // { dg-error "" "" { target { ! c++17 } } }
+struct Y<T, v> { }; // { dg-error "" }
 
 
 template<typename T, T V>
diff --git a/gcc/testsuite/g++.dg/template/ttp33.C b/gcc/testsuite/g++.dg/template/ttp33.C
new file mode 100644
index 00000000000..cd0de8ca641
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/ttp33.C
@@ -0,0 +1,10 @@
+// A slight variation of ttp31.C.
+// { dg-do compile { target c++11 } }
+
+template<class TA,
+	 template<typename TA::type...> class TTA, TA... VA>
+struct A { };
+
+template<class UC, class TC,
+	 template<typename TC::type...> class TTC, TC... VC>
+struct C : A<TC, TTC, VC...> { };