diff --git a/src/Database/Esqueleto/Utils.hs b/src/Database/Esqueleto/Utils.hs
index c0b80448e..127e0ed88 100644
--- a/src/Database/Esqueleto/Utils.hs
+++ b/src/Database/Esqueleto/Utils.hs
@@ -17,7 +17,7 @@ module Database.Esqueleto.Utils
   , (>~.), (<~.)
   , or, and
   , any, all
-  -- , parens
+  , not__, parens
   , subSelectAnd, subSelectOr
   , mkExactFilter, mkExactFilterWith, mkExactFilterWithComma
   , mkExactFilterLast, mkExactFilterLastWith
@@ -253,6 +253,9 @@ subSelectOr  q = parens . E.subSelectUnsafe $ flip (E.unsafeSqlAggregateFunction
 parens :: E.SqlExpr (E.Value a) -> E.SqlExpr (E.Value a)
 parens = E.unsafeSqlFunction ""
 
+-- | Workaround for Esqueleto-Bug not placing parenthesis after NOT, see #155
+not__ :: E.SqlExpr (E.Value Bool) -> E.SqlExpr (E.Value Bool)
+not__ = E.not_ . parens
 
 -- Allow usage of Tuples as DbtRowKey, i.e. SqlIn instances for tuples
 $(sqlInTuples [2..16])
diff --git a/src/Handler/Utils/Users.hs b/src/Handler/Utils/Users.hs
index 5c85c9c73..e281c7fcf 100644
--- a/src/Handler/Utils/Users.hs
+++ b/src/Handler/Utils/Users.hs
@@ -189,7 +189,7 @@ guessUser (((Set.toList . toNullable) <$>) . Set.toList . dnfTerms -> criteria)
 
     containsAsSet x y = E.and . map (\y' -> x `E.hasInfix` E.val y') $ asWords y
 
-    toSql user pl = bool id E.not_ (is _PLNegated pl) $ case pl ^. _plVar of
+    toSql user pl = bool id E.not__ (is _PLNegated pl) $ case pl ^. _plVar of
       GuessUserMatrikelnummer         userMatriculation' -> user E.^. UserMatrikelnummer  E.==.          E.val (Just userMatriculation')
       GuessUserEduPersonPrincipalName userEPPN'          -> user E.^. UserLdapPrimaryKey  E.==.          E.val (Just userEPPN')
       GuessUserDisplayName            userDisplayName'   -> user E.^. UserDisplayName    `containsAsSet` userDisplayName'
diff --git a/src/Jobs/Handler/LMS.hs b/src/Jobs/Handler/LMS.hs
index 013f849b7..136ea518e 100644
--- a/src/Jobs/Handler/LMS.hs
+++ b/src/Jobs/Handler/LMS.hs
@@ -202,7 +202,7 @@ dispatchJobLmsDequeue qid = JobHandlerAtomic act
               -- E.&&.  luser E.?. LmsUserQualification        E.?=. E.val qid
               -- E.&&.  E.isNothing (luser E.^. LmsUserStatus)
               -- E.&&.  E.isNothing (luser E.^. LmsUserEnded)
-              E.&&.  E.not_ (validQualification now quser)
+              E.&&.  E.not__ (validQualification now quser)
           pure (luser E.?. LmsUserId, quser E.^. QualificationUserUser)
       nrBlocked <- qualificationUserBlocking qid (E.unValue . snd <$> expiredUsers) False (Just now) (Right QualificationBlockExpired) True -- essential that blocks occur only once
       let expiredLearners = [ luid | (E.Value (Just luid), _) <- expiredUsers ]
@@ -223,7 +223,7 @@ dispatchJobLmsDequeue qid = JobHandlerAtomic act
               `E.on` (\(quser :& qblock) -> qblock E.?. QualificationUserBlockQualificationUser E.?=. quser E.^. QualificationUserId
                         E.&&. qblock `isLatestBlockBefore` E.val now
                      )
-            E.where_ $ -- E.not_ (validQualification now quser)                   -- currently invalid
+            E.where_ $ -- E.not__ (validQualification now quser)                   -- currently invalid
                     quser E.^. QualificationUserQualification E.==. E.val qid  -- correct qualification
               E.&&. quserToNotify now quser qblock                            -- recently became invalid or blocked
             pure (quser E.^. QualificationUserUser)