diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e3c11fe0372..620a3105c1c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2015-11-18  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR bootstrap/68406
+	* hash-set.h (hash_set::traverse): Expand Key typedef.
+
 2015-11-18  Martin Liska  <mliska@suse.cz>
 
 	* config/arm/arm.c (arm_valid_target_attribute_p): Finalize
diff --git a/gcc/hash-set.h b/gcc/hash-set.h
index 679d2b6df64..8a7c9a00c17 100644
--- a/gcc/hash-set.h
+++ b/gcc/hash-set.h
@@ -68,7 +68,7 @@ public:
   /* Call the call back on each pair of key and value with the passed in
      arg.  */
 
-  template<typename Arg, bool (*f)(const Key &, Arg)>
+  template<typename Arg, bool (*f)(const typename Traits::value_type &, Arg)>
   void traverse (Arg a) const
     {
       for (typename hash_table<Traits>::iterator iter = m_table.begin ();