diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index a6d47af..76a74fb 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -546,7 +546,7 @@
     def test_initgroups(self):
         # find missing group
 
-        g = max(self.saved_groups) + 1
+        g = max(self.saved_groups or [0]) + 1
         name = pwd.getpwuid(posix.getuid()).pw_name
         posix.initgroups(name, g)
         self.assertIn(g, posix.getgroups())