diff --git a/CHANGELOG b/CHANGELOG
index 7229bcca5..2d971ddd8 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -102,7 +102,7 @@ Other:
 - Accelerated startup process (send all data to the client after login).
 - Added function utils.auth.anonymous_is_enabled which returns true, if it is.
 - Changed has_perm to support an user id or None (for anyonmous) as first argument.
-- Removed our AnonymousUser. Please make sure not to use user.has_perm() anymore.
+- Removed our AnonymousUser. Make sure not to use user.has_perm() anymore.
 
 
 Version 2.0 (2016-04-18)
diff --git a/openslides/users/models.py b/openslides/users/models.py
index 7cc49008c..51c8741cc 100644
--- a/openslides/users/models.py
+++ b/openslides/users/models.py
@@ -216,6 +216,12 @@ class User(RESTModelMixin, PermissionsMixin, AbstractBaseUser):
             self.structure_level,
             self.about_me))
 
+    def has_perm(self, perm):
+        """
+        This method is closed. Do not use it but use openslides.utils.auth.has_perm.
+        """
+        raise RuntimeError('Do not use user.has_perm() but use openslides.utils.auth.has_perm')
+
 
 class GroupManager(GroupManager):
     """
diff --git a/openslides/utils/auth.py b/openslides/utils/auth.py
index 73de6dde4..ca22c322d 100644
--- a/openslides/utils/auth.py
+++ b/openslides/utils/auth.py
@@ -8,22 +8,24 @@ def has_perm(user, perm):
     """
     Checks that user has a specific permission.
 
-    User can be an a CollectionElement for a user or None.
+    User can be a CollectionElement of a user or None.
     """
+    group_collection_string = 'users/group'  # This is the hard coded collection string for openslides.users.models.Group
+
     # Convert user to right type
     user = user_to_collection_user(user)
     if user is None and not anonymous_is_enabled():
         has_perm = False
     elif user is None:
-        # Use the permissions from the default group.
-        default_group = CollectionElement.from_values('users/group', 1)
+        # Use the permissions from the default group with id 1.
+        default_group = CollectionElement.from_values(group_collection_string, 1)
         has_perm = perm in default_group.get_full_data()['permissions']
     else:
         # Get all groups of the user and then see, if one group has the required
         # permission. If the user has no groups, then use group 1.
         group_ids = user.get_full_data()['groups_id'] or [1]
         for group_id in group_ids:
-            group = CollectionElement.from_values('users/group', group_id)
+            group = CollectionElement.from_values(group_collection_string, group_id)
             if perm in group.get_full_data()['permissions']:
                 has_perm = True
                 break
@@ -34,7 +36,7 @@ def has_perm(user, perm):
 
 def anonymous_is_enabled():
     """
-    Returns true, when the anonymous user is enabled in the settings.
+    Returns True if the anonymous user is enabled in the settings.
     """
     return (CollectionElement.from_values('core/config', 'general_system_enable_anonymous')
             .get_full_data()['value'])
@@ -42,21 +44,23 @@ def anonymous_is_enabled():
 
 def user_to_collection_user(user):
     """
-    Taks an object, that represents a user an converts it to a collection_element
-    or None, if it is an anonymous user.
+    Takes an object, that represents a user and converts it to a CollectionElement
+    or to None, if it is an anonymous user.
 
     User can be
-    * a user object,
-    * a collection_element for an user
-    * an user id
+    * an user object,
+    * a CollectionElement of an user,
+    * an user id or
     * an anonymous user.
 
-    Raises an TypeError, if the given user object can not be converted
+    Raises an TypeError, if the given user object can not be converted.
     """
+    User = get_user_model()
+
     if user is None:
         # Nothing to do
         pass
-    elif isinstance(user, CollectionElement) and user.collection_string == 'users/user':
+    elif isinstance(user, CollectionElement) and user.collection_string == User.get_collection_string():
         # Nothing to do
         pass
     elif isinstance(user, CollectionElement):
@@ -64,15 +68,15 @@ def user_to_collection_user(user):
             "Unsupported type for user. Only CollectionElements for users can be"
             "used. Not {}".format(user.collection_string))
     elif isinstance(user, int):
-        user = CollectionElement.from_values('users/user', user)
+        user = CollectionElement.from_values(User.get_collection_string(), user)
     elif isinstance(user, AnonymousUser):
         user = None
-    elif isinstance(user, get_user_model()):
+    elif isinstance(user, User):
         # Converts a user object to a collection element.
         # from_instance can not be used because the user serializer loads
-        # the group from the db. So each call to from_instance(user) consts
+        # the group from the db. So each call to from_instance(user) costs
         # one db query.
-        user = CollectionElement.from_values('users/user', user.id)
+        user = CollectionElement.from_values(User.get_collection_string(), user.id)
     else:
         raise TypeError(
             "Unsupported type for user. User {} has type {}.".format(user, type(user)))