diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7499992a73a..bf995f0e8ef 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-26  Jason Merrill  <jason@redhat.com>
+
+	PR c++/84551 - ICE with concepts and -g.
+	* parser.c (add_debug_begin_stmt): Do nothing in a concept.
+
 2018-02-26  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/84325
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 4fa546a086c..f305c9c7eba 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -10699,6 +10699,9 @@ add_debug_begin_stmt (location_t loc)
 {
   if (!MAY_HAVE_DEBUG_MARKER_STMTS)
     return;
+  if (DECL_DECLARED_CONCEPT_P (current_function_decl))
+    /* A concept is never expanded normally.  */
+    return;
 
   tree stmt = build0 (DEBUG_BEGIN_STMT, void_type_node);
   SET_EXPR_LOCATION (stmt, loc);
diff --git a/gcc/testsuite/g++.dg/concepts/debug1.C b/gcc/testsuite/g++.dg/concepts/debug1.C
new file mode 100644
index 00000000000..eeb63654243
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/debug1.C
@@ -0,0 +1,10 @@
+// PR c++/84551
+// { dg-options "-g -O -std=c++17 -fconcepts" }
+
+template<typename> concept bool C() { return true; }
+
+template<template<typename T> requires C<T>() class> struct A {};
+
+template<typename> requires true struct B {};
+
+A<B> a;