1 files changed, 5 insertions, 0 deletions
diff --git a/hash.c b/hash.c
index 0328d9d1aa..c3b07442ff 100644
--- a/hash.c
+++ b/hash.c
@@ -1673,6 +1673,11 @@ rb_hash_flatten(int argc, VALUE *argv, VALUE hash)
     VALUE ary;
 
     ary = rb_hash_to_a(hash);
+    if (argc == 0) {
+	argc = 1;
+	tmp = INT2FIX(1);
+	argv = &tmp;
+    }
     rb_funcall2(ary, rb_intern("flatten!"), argc, argv);
     return ary;
 }