diff --git a/src/Model/Migration.hs b/src/Model/Migration.hs
index e7ad3c9af..bd957ffe1 100644
--- a/src/Model/Migration.hs
+++ b/src/Model/Migration.hs
@@ -524,21 +524,31 @@ customMigrations = Map.fromListWith (>>)
         runConduit $ getExamEntries .| C.mapM_ renameExamParts
     )
   , ( AppliedMigrationKey [migrationVersion|21.0.0|] [version|22.0.0|]
-    , whenM (tableExists "exam") $
-        [executeQQ|
-          ALTER TABLE "exam" DROP COLUMN IF EXISTS "grading_key";
-          ALTER TABLE "exam" ADD COLUMN IF NOT EXISTS "grading_rule" jsonb;
+    , whenM (tableExists "exam") $ do
+        oldVersion <- columnExists "exam" "grading_key"
+        if
+          | oldVersion -> do
+            -- Major changes happend to the structure of exams without appropriate
+            -- migration, try to remedy that here
+            tableDropEmpty "exam_part_corrector"
+            tableDropEmpty "exam_corrector"
+            tableDropEmpty "exam_result"
+            tableDropEmpty "exam_registration"
+            tableDropEmpty "exam_occurrence"
+            tableDropEmpty "exam_part"
+            tableDropEmpty "exam"
+          | otherwise ->
+            [executeQQ|
+              ALTER TABLE "exam" ALTER COLUMN "grading_rule" DROP NOT NULL;
+              ALTER TABLE "exam" ALTER COLUMN "bonus_rule" DROP NOT NULL;
+              ALTER TABLE "exam" ALTER COLUMN "occurrence_rule" DROP NOT NULL;
 
-          ALTER TABLE "exam" ALTER COLUMN "grading_rule" DROP NOT NULL;
-          ALTER TABLE "exam" ALTER COLUMN "bonus_rule" DROP NOT NULL;
-          ALTER TABLE "exam" ALTER COLUMN "occurrence_rule" DROP NOT NULL;
+              UPDATE "exam" SET "grading_rule" = NULL WHERE "grading_rule" = '{ "rule": "manual" }';
+              UPDATE "exam" SET "bonus_rule" = NULL WHERE "bonus_rule" = '{ "rule": "no-bonus"}';
+              UPDATE "exam" SET "occurrence_rule" = NULL WHERE "occurrence_rule" = '"manual"';
 
-          UPDATE "exam" SET "grading_rule" = NULL WHERE "grading_rule" = '{ "rule": "manual" }';
-          UPDATE "exam" SET "bonus_rule" = NULL WHERE "bonus_rule" = '{ "rule": "no-bonus"}';
-          UPDATE "exam" SET "occurrence_rule" = NULL WHERE "occurrence_rule" = '"manual"';
-
-          UPDATE "exam" SET "occurrence_rule" = json_build_object('rule', "occurrence_rule");
-        |]
+              UPDATE "exam" SET "occurrence_rule" = json_build_object('rule', "occurrence_rule");
+            |]
     )
   ]
 
diff --git a/src/Utils.hs b/src/Utils.hs
index f257bc312..ca5330ea6 100644
--- a/src/Utils.hs
+++ b/src/Utils.hs
@@ -979,5 +979,5 @@ clampMin, clampMax :: Ord a
                    => a -- ^ Boundary
                    -> a -- ^ Value
                    -> a -- ^ Clamped Value
-clampMin minVal = max minVal
-clampMax maxVal = min maxVal
+clampMin = max
+clampMax = min
diff --git a/test/Model/TypesSpec.hs b/test/Model/TypesSpec.hs
index 49faef34f..c27083034 100644
--- a/test/Model/TypesSpec.hs
+++ b/test/Model/TypesSpec.hs
@@ -240,8 +240,7 @@ instance Arbitrary ExamGrade where
 
 instance Arbitrary ExamGradingRule where
   arbitrary = oneof
-    [ pure ExamGradingManual
-    , ExamGradingKey . reverse . fromOffsets . map getNonNegative <$> replicateM 11 arbitrary
+    [ ExamGradingKey . reverse . fromOffsets . map getNonNegative <$> replicateM 10 arbitrary
     ]
     where
       fromOffsets [] = []