diff --git a/models/exams.model b/models/exams.model
index 27bdba1d8..0abad27a3 100644
--- a/models/exams.model
+++ b/models/exams.model
@@ -35,7 +35,7 @@ ExamOccurrence
   name ExamOccurrenceName
   room RoomReference Maybe
   roomHidden Bool default=false
-  capacity Word64 
+  capacity Word64 Maybe
   start UTCTime
   end UTCTime Maybe
   description StoredMarkup Maybe
@@ -79,4 +79,4 @@ ExamPartCorrector
 ExamOfficeSchool
   school SchoolId
   exam ExamId
-  UniqueExamOfficeSchool exam school
\ No newline at end of file
+  UniqueExamOfficeSchool exam school