diff --git a/amivapi/studydocs/model.py b/amivapi/studydocs/model.py
index ef5397e1..1717cbc6 100644
--- a/amivapi/studydocs/model.py
+++ b/amivapi/studydocs/model.py
@@ -182,9 +182,9 @@ def _validate_allow_summary(self, *args, **kwargs):
             'type': {
                 'example': 'cheat sheets',
                 'type': 'string',
-                'nullable': True,
-                'default': None,
-                'allowed': ['exams', 'oral exams',
+                'required': True,
+                'nullable': False,
+                'allowed': ['spring exams', 'autumn exams', 'oral exams',
                             'cheat sheets', 'study guides',
                             'lecture documents', 'exercises'],
                 'allow_summary': True,