Correction to issue 17052 fix
diff --git a/Lib/unittest/main.py b/Lib/unittest/main.py
index 1e001a6..b253679 100644
--- a/Lib/unittest/main.py
+++ b/Lib/unittest/main.py
@@ -159,7 +159,7 @@
 
     def _do_discovery(self, argv, Loader=None):
         if Loader is None:
-            Loader = self.testLoader
+            Loader = lambda: self.testLoader
 
         # handle command line args for test discovery
         self.progName = '%s discover' % self.progName