diff --git a/test/resolv/test_dns.rb b/test/resolv/test_dns.rb
index 1ac3aea7b8..d75a431bcc 100644
--- a/test/resolv/test_dns.rb
+++ b/test/resolv/test_dns.rb
@@ -212,8 +212,8 @@ class TestResolvDNS < Test::Unit::TestCase
 
   def test_ipv6_create
     ref = '[Bug #11910] [ruby-core:72559]'
-    assert_instance_of Resolv::IPv6, Resolv::IPv6.create('::1')
-    assert_instance_of Resolv::IPv6, Resolv::IPv6.create('::1:127.0.0.1')
+    assert_instance_of Resolv::IPv6, Resolv::IPv6.create('::1'), ref
+    assert_instance_of Resolv::IPv6, Resolv::IPv6.create('::1:127.0.0.1'), ref
   end
 
   def test_ipv6_should_be_16