diff --git a/lib/resolv.rb b/lib/resolv.rb
index 9a981b9..f99f5aa 100644
--- a/lib/resolv.rb
+++ b/lib/resolv.rb
@@ -706,7 +706,7 @@ def request(sender, tout)
           rescue DecodeError
             next # broken DNS message ignored
           end
-          if s = sender_for(from, msg)
+          if (s = sender_for(from, msg)) && s == sender
             break
           else
             # unexpected DNS message ignored