diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 26b8d81..c04c679 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -427,7 +427,7 @@
             groups = idg.read().strip()
             ret = idg.close()
 
-        if ret != 0 or not groups:
+        if ret != None or not groups:
             raise unittest.SkipTest("need working 'id -G'")
 
         # 'id -G' and 'os.getgroups()' should return the same