diff --git a/radicale/acl/PAM.py b/radicale/acl/PAM.py
index 3399a3c..d9c84e1 100644
--- a/radicale/acl/PAM.py
+++ b/radicale/acl/PAM.py
@@ -50,7 +50,7 @@ def has_right(owner, user, password):
 
     # Check whether the group exists
     try:
-        members = grp.getgrnam(GROUP_MEMBERSHIP)
+        members = grp.getgrnam(GROUP_MEMBERSHIP).gr_mem
     except KeyError:
         log.LOGGER.debug(
             "The PAM membership required group (%s) doesn't exist" %