diff --git a/lib/test/unit.rb b/lib/test/unit.rb
index 2d25f2f2c3..518ce04e7e 100644
--- a/lib/test/unit.rb
+++ b/lib/test/unit.rb
@@ -656,7 +656,7 @@ module Test
       alias mini_run_suite _run_suite
 
       def output
-        @output || super
+        (@output ||= nil) || super
       end
 
       def _prepare_run(suites, type)