diff --git a/test/psych/test_object_references.rb b/test/psych/test_object_references.rb
index 77cc96e29d..2a659a3ae6 100644
--- a/test/psych/test_object_references.rb
+++ b/test/psych/test_object_references.rb
@@ -28,7 +28,7 @@ module Psych
 
     def assert_reference_trip obj
       yml = Psych.dump([obj, obj])
-      assert_match(/\*\d+/, yml)
+      assert_match(/\*-?\d+/, yml)
       data = Psych.load yml
       assert_equal data.first.object_id, data.last.object_id
     end