diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index f73ea2a1f3e..fdc1247746d 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-18  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/85065
+	* cp-tree.h (NON_ERROR): New.
+	* pt.c (auto_hash::hash): Use it.
+	(do_auto_deduction): Likewise.
+
 2018-09-18  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/86881
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 6cd6e5f5886..2203e92dda8 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1877,6 +1877,8 @@ struct GTY(()) language_function {
 /* In parser.c.  */
 extern tree cp_literal_operator_id (const char *);
 
+#define NON_ERROR(NODE) ((NODE) == error_mark_node ? NULL_TREE : (NODE))
+
 /* TRUE if a tree code represents a statement.  */
 extern bool statement_code_p[MAX_TREE_CODES];
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 892a387cbc5..b8b6545434b 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -26121,7 +26121,7 @@ struct auto_hash : default_hash_traits<tree>
 inline hashval_t
 auto_hash::hash (tree t)
 {
-  if (tree c = PLACEHOLDER_TYPE_CONSTRAINTS (t))
+  if (tree c = NON_ERROR (PLACEHOLDER_TYPE_CONSTRAINTS (t)))
     /* Matching constrained-type-specifiers denote the same template
        parameter, so hash the constraint.  */
     return hash_placeholder_constraint (c);
@@ -26880,7 +26880,7 @@ do_auto_deduction (tree type, tree init, tree auto_node,
 
   /* Check any placeholder constraints against the deduced type. */
   if (flag_concepts && !processing_template_decl)
-    if (tree constr = PLACEHOLDER_TYPE_CONSTRAINTS (auto_node))
+    if (tree constr = NON_ERROR (PLACEHOLDER_TYPE_CONSTRAINTS (auto_node)))
       {
         /* Use the deduced type to check the associated constraints. If we
            have a partial-concept-id, rebuild the argument list so that
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3c96db42b62..7a7a7c24563 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-18  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/85065
+	* g++.dg/concepts/pr85065.C: New.
+
 2018-09-18  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	PR testsuite/87339
@@ -11,10 +16,10 @@
 
 2018-09-18  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
-    * gcc.target/aarch64/spellcheck_1.c:
-    Make architecture suggestion optional.
-    * gcc.target/aarch64/spellcheck_4.c:
-    Likewise.
+	* gcc.target/aarch64/spellcheck_1.c:
+	Make architecture suggestion optional.
+	* gcc.target/aarch64/spellcheck_4.c:
+	Likewise.
 
 2018-09-18  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
diff --git a/gcc/testsuite/g++.dg/concepts/pr85065.C b/gcc/testsuite/g++.dg/concepts/pr85065.C
new file mode 100644
index 00000000000..861a838dd29
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/pr85065.C
@@ -0,0 +1,6 @@
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-fconcepts" }
+
+template<int> concept bool C = true;
+
+C c = 0;  // { dg-error "invalid reference to concept" }