diff --git a/src/milla/auth/permissions.py b/src/milla/auth/permissions.py
index 8598216..00a78e0 100644
--- a/src/milla/auth/permissions.py
+++ b/src/milla/auth/permissions.py
@@ -49,7 +49,7 @@ class PermissionContainer(object):
         for perm in self._group_perms:
             yield perm
     
-    def __in__(self, perm):
+    def __contains__(self, perm):
         return perm in self._user_perms or perm in self._group_perms