diff --git a/src/Foundation/Authorization.hs b/src/Foundation/Authorization.hs
index cd5f4be14..7fc4f1794 100644
--- a/src/Foundation/Authorization.hs
+++ b/src/Foundation/Authorization.hs
@@ -1505,7 +1505,8 @@ tagAccessPredicate AuthCapacity = APDB $ \_ _ _ route _ -> case route of
     eid <- $cachedHereBinary (cid, examn) . MaybeT . getKeyBy $ UniqueExam cid examn
     Entity occId ExamOccurrence{..} <- $cachedHereBinary (eid, occn) . MaybeT . getBy $ UniqueExamOccurrence eid occn
     registered <- $cachedHereBinary occId . lift $ fromIntegral <$> count [ ExamRegistrationOccurrence ==. Just occId, ExamRegistrationExam ==. eid ]
-    guard $ examOccurrenceCapacity > registered
+    -- Nothing means unlimited size
+    guard $ maybe True (> registered) examOccurrenceCapacity
     return Authorized
   CTutorialR tid ssh csh tutn _ -> maybeT (unauthorizedI MsgTutorialNoCapacity) $ do
     cid <- $cachedHereBinary (tid, ssh, csh) . MaybeT . getKeyBy $ TermSchoolCourseShort tid ssh csh
diff --git a/src/Handler/Exam/Form.hs b/src/Handler/Exam/Form.hs
index f4dfdbe08..876687260 100644
--- a/src/Handler/Exam/Form.hs
+++ b/src/Handler/Exam/Form.hs
@@ -59,7 +59,7 @@ data ExamOccurrenceForm = ExamOccurrenceForm
   , eofName :: ExamOccurrenceName
   , eofRoom :: Maybe RoomReference
   , eofRoomHidden :: Bool
-  , eofCapacity :: Word64
+  , eofCapacity :: Maybe Word64
   , eofStart :: UTCTime
   , eofEnd :: Maybe UTCTime
   , eofDescription :: Maybe StoredMarkup
@@ -232,7 +232,7 @@ examOccurrenceForm prev = wFormToAForm $ do
         <*> apopt checkBoxField (fslI MsgExamRoomRoomHidden & setTooltip MsgExamRoomRoomHiddenTip & addName (nudge "room-hidden")) (eofRoomHidden <$> mPrev)
       let eofRoomRes = view _1 <$> eofRoomRes'
           eofRoomHiddenRes = view _2 <$> eofRoomRes'
-      (eofCapacityRes, eofCapacityView) <- mpreq (natFieldI MsgExamRoomCapacityNegative) (fslI MsgExamRoomCapacity & addName (nudge "capacity")) (eofCapacity <$> mPrev)
+      (eofCapacityRes, eofCapacityView) <- mopt (natFieldI MsgExamRoomCapacityNegative) (fslI MsgExamRoomCapacity & addName (nudge "capacity")) (eofCapacity <$> mPrev)
       (eofStartRes, eofStartView) <- mpreq utcTimeField (fslI MsgExamRoomStart & addName (nudge "start")) (eofStart <$> mPrev)
       (eofEndRes, eofEndView) <- mopt utcTimeField (fslI MsgExamRoomEnd & addName (nudge "end")) (eofEnd <$> mPrev)
       (eofDescRes, eofDescView) <- mopt htmlField (fslI MsgExamRoomDescription & addName (nudge "description")) (eofDescription <$> mPrev)