diff --git a/src/Handler/Allocation/Show.hs b/src/Handler/Allocation/Show.hs
index 6cbd6250c..432566344 100644
--- a/src/Handler/Allocation/Show.hs
+++ b/src/Handler/Allocation/Show.hs
@@ -105,7 +105,7 @@ postAShowR tid ssh ash = do
     return (alloc, school, isAnyLecturer, isAdmin, nubOn (view $ resultCourse . _entityKey) courses, registration, wouldNotifyNewCourse)
 
   let nextSubstitutesDeadline = minimumOf (folded . resultAllocationCourse . _allocationCourseAcceptSubstitutes . _Just . filtered (>= now)) courses
-      freeCapacity = fmap getSum . getAp . flip foldMap courses $ \cEntry -> Ap . fmap (Sum . max 0) $ (subtract $ cEntry ^. resultParticipantCount) <$> preview (resultCourse . _entityVal . _courseCapacity . _Just) cEntry
+      freeCapacity = fmap getSum . getAp . flip foldMap courses $ \cEntry -> Ap . fmap (Sum . max 0) $ subtract (cEntry ^. resultParticipantCount) <$> preview (resultCourse . _entityVal . _courseCapacity . _Just) cEntry
 
   MsgRenderer mr <- getMsgRenderer
   let title = MsgAllocationTitle (mr . ShortTermIdentifier $ unTermKey allocationTerm) (unSchoolKey allocationSchool) allocationName