diff --git a/hash.c b/hash.c
index 007508a3c5..61f64101d3 100644
--- a/hash.c
+++ b/hash.c
@@ -1756,7 +1756,7 @@ keys_i(VALUE key, VALUE value, VALUE ary)
  *
  */
 
-static VALUE
+VALUE
 rb_hash_keys(VALUE hash)
 {
     VALUE keys;
diff --git a/internal.h b/internal.h
index 5a89da41d6..9b5fb0d0bb 100644
--- a/internal.h
+++ b/internal.h
@@ -596,6 +596,7 @@ void rb_gc_resurrect(VALUE ptr);
 /* hash.c */
 struct st_table *rb_hash_tbl_raw(VALUE hash);
 #define RHASH_TBL_RAW(h) rb_hash_tbl_raw(h)
+VALUE rb_hash_keys(VALUE hash);
 VALUE rb_hash_values(VALUE hash);
 #define HASH_DELETED  FL_USER1
 #define HASH_PROC_DEFAULT FL_USER2