diff --git a/bootstraptest/test_thread.rb b/bootstraptest/test_thread.rb
index 048aeb19c2..d64f44be49 100644
--- a/bootstraptest/test_thread.rb
+++ b/bootstraptest/test_thread.rb
@@ -85,7 +85,7 @@ assert_equal %q{ok}, %q{
       ans = :ok
     end
   }
-  Thread.pass
+  Thread.pass until t.stop?
   t.kill
   t.join
   ans