diff --git a/KNOWNBUGS.rb b/KNOWNBUGS.rb
index 1b170b6712..9fe4c29cf5 100644
--- a/KNOWNBUGS.rb
+++ b/KNOWNBUGS.rb
@@ -4,6 +4,8 @@
 #
 
 assert_normal_exit(<<'End', '[ruby-dev:37934]')
+  Thread.new { sleep 1; Thread.kill Thread.main }
   Process.setrlimit(:NPROC, 1)
-  system("ls")
+  fork {}
 End
+