diff --git a/src/Handler/Utils/Exam.hs b/src/Handler/Utils/Exam.hs
index c7abfacb5..a676f61ae 100644
--- a/src/Handler/Utils/Exam.hs
+++ b/src/Handler/Utils/Exam.hs
@@ -1,5 +1,4 @@
 {-# OPTIONS_GHC -fno-warn-incomplete-uni-patterns #-}
-{-# OPTIONS_GHC -Wwarn #-}
 
 module Handler.Utils.Exam
   ( fetchExamAux
@@ -28,15 +27,15 @@ import Database.Esqueleto.Utils.TH
 import qualified Data.Conduit.List as C
 
 import qualified Data.Map as Map
+import qualified Data.Map.Merge.Lazy as Map
 import qualified Data.Set as Set
 
 import qualified Data.Foldable as F
 
 import qualified Data.CaseInsensitive as CI
 
-import Control.Monad.Trans.Random.Lazy (evalRand)
 import System.Random (mkStdGen)
-import Control.Monad.Random.Class (weighted)
+import System.Random.Shuffle (shuffle')
 import Control.Monad.ST (ST, runST)
 
 import Data.Array (Array)
@@ -49,6 +48,7 @@ import Data.List (findIndex, unfoldr)
 import qualified Data.List as List
 
 import Data.ExtendedReal
+import Data.Ratio (Ratio())
 
 import qualified Data.RFC5051 as RFC5051
 
@@ -265,7 +265,7 @@ examAutoOccurrence :: forall seed.
                    -> Map ExamOccurrenceId Natural
                    -> Map UserId (User, Maybe ExamOccurrenceId)
                    -> (Maybe (ExamOccurrenceMapping ExamOccurrenceId), Map UserId (Maybe ExamOccurrenceId))
-examAutoOccurrence (hash -> seed) rule config@ExamAutoOccurrenceConfig{..} occurrences users
+examAutoOccurrence (hash -> seed) rule ExamAutoOccurrenceConfig{..} occurrences users
   | sum occurrences' < usersCount
     || sum occurrences' <= 0
     || Map.null users'