diff --git a/tool/lib/test/unit.rb b/tool/lib/test/unit.rb
index 6175b2a531..0b352060af 100644
--- a/tool/lib/test/unit.rb
+++ b/tool/lib/test/unit.rb
@@ -416,6 +416,7 @@ module Test
 
         def kill
           Process.kill(:KILL, @pid)
+          warn "worker #{@pid} does not respond; SIGKILL is sent"
         rescue Errno::ESRCH
         end