diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 2a5051c7b43..72fbdab06c5 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1203,7 +1203,7 @@ maybe_initialize_constexpr_call_table (void)
 
    This is not GC-deletable to avoid GC affecting UID generation.  */
 
-static GTY(()) hash_map<tree, tree> *fundef_copies_table;
+static GTY(()) decl_tree_map *fundef_copies_table;
 
 /* Reuse a copy or create a new unshared copy of the function FUN.
    Return this copy.  We use a TREE_LIST whose PURPOSE is body, VALUE
diff --git a/gcc/tree.h b/gcc/tree.h
index b0ef14b6cd9..9ec24a3008b 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -5453,6 +5453,11 @@ struct type_tree_cache_traits
   : simple_cache_map_traits<tree_type_hash, tree> { };
 typedef hash_map<tree,tree,type_tree_cache_traits> type_tree_cache_map;
 
+/* Similarly to decl_tree_cache_map, but without caching.  */
+struct decl_tree_traits
+  : simple_hashmap_traits<tree_decl_hash, tree> { };
+typedef hash_map<tree,tree,decl_tree_traits> decl_tree_map;
+
 /* Initialize the abstract argument list iterator object ITER with the
    arguments from CALL_EXPR node EXP.  */
 static inline void