diff --git a/esqueleto.cabal b/esqueleto.cabal
--- a/esqueleto.cabal
+++ b/esqueleto.cabal
@@ -1,5 +1,5 @@
 name:                esqueleto
-version:             2.5.0
+version:             2.5.1
 synopsis:            Type-safe EDSL for SQL queries on persistent backends.
 homepage:            https://github.com/bitemyapp/esqueleto
 license:             BSD3
@@ -36,7 +36,7 @@
   Not all SQL features are available, but most of them can be easily added
   (especially functions), so please open an issue or send a pull request if
   you need anything that is not covered by @esqueleto@ on
-  <https://github.com/prowdsponsor/esqueleto/>.
+  <https://github.com/bitemyapp/esqueleto>.
   .
   The name of this library means \"skeleton\" in Portuguese and
   contains all three SQL letters in the correct order =).  It was
@@ -44,7 +44,7 @@
 
 source-repository head
   type:     git
-  location: git://github.com/prowdsponsor/esqueleto.git
+  location: git://github.com/bitemyapp/esqueleto.git
 
 Flag postgresql
   Description: test postgresql. default is to test sqlite.
@@ -63,10 +63,10 @@
   other-modules:
     Database.Esqueleto.Internal.PersistentImport
   build-depends:
-      base                 >= 4.5     && < 4.9
+      base                 >= 4.5     && < 5.0
     , bytestring
     , text                 >= 0.11    && < 1.3
-    , persistent           >= 2.5 && < 2.6
+    , persistent           >= 2.5 && < 2.7
     , transformers         >= 0.2
     , unordered-containers >= 0.2
     , tagged               >= 0.2
@@ -76,7 +76,10 @@
     , resourcet            >= 1.1
     , blaze-html
   hs-source-dirs: src/
-  ghc-options: -Wall
+  if impl(ghc >= 8.0)
+    ghc-options: -Wall -Wno-redundant-constraints
+  else
+    ghc-options: -Wall
 
 test-suite test
   type: exitcode-stdio-1.0
diff --git a/src/Database/Esqueleto.hs b/src/Database/Esqueleto.hs
--- a/src/Database/Esqueleto.hs
+++ b/src/Database/Esqueleto.hs
@@ -14,14 +14,14 @@
 -- @
 -- -- For a module that mostly uses esqueleto.
 -- import Database.Esqueleto
--- import qualified Database.Persistent as P
+-- import qualified Database.Persist as P
 -- @
 --
 -- or import @esqueleto@ itself qualified:
 --
 -- @
 -- -- For a module that uses esqueleto just on some queries.
--- import Database.Persistent
+-- import Database.Persist
 -- import qualified Database.Esqueleto as E
 -- @
 --
diff --git a/src/Database/Esqueleto/Internal/Language.hs b/src/Database/Esqueleto/Internal/Language.hs
--- a/src/Database/Esqueleto/Internal/Language.hs
+++ b/src/Database/Esqueleto/Internal/Language.hs
@@ -44,7 +44,6 @@
   , else_
   ) where
 
-import Control.Applicative (Applicative(..), (<$>))
 import Control.Exception (Exception)
 import Data.Int (Int64)
 import Data.Typeable (Typeable)
@@ -52,7 +51,6 @@
 import Text.Blaze.Html (Html)
 
 import qualified Data.ByteString as B
-import qualified Data.ByteString.Lazy as BL
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as TL
 
@@ -471,7 +469,7 @@
   -- @
   -- select $
   -- 'from' $ \\person -> do
-  -- 'where_' $ person '^.' PersonId ``in_'` 'valList' personIds
+  -- 'where_' $ person '^.' PersonId `'in_`` 'valList' personIds
   -- return person
   -- @
   --
diff --git a/src/Database/Esqueleto/Internal/PersistentImport.hs b/src/Database/Esqueleto/Internal/PersistentImport.hs
--- a/src/Database/Esqueleto/Internal/PersistentImport.hs
+++ b/src/Database/Esqueleto/Internal/PersistentImport.hs
@@ -5,7 +5,7 @@
   ) where
 
 import Database.Persist.Sql hiding
-  ( BackendSpecificFilter, Filter(..), PersistQuery(..), SelectOpt(..)
+  ( BackendSpecificFilter, Filter(..), PersistQuery, SelectOpt(..)
   , Update(..), delete, deleteWhereCount, updateWhereCount, selectList
   , selectKeysList, deleteCascadeWhere, (=.), (+=.), (-=.), (*=.), (/=.)
   , (==.), (!=.), (<.), (>.), (<=.), (>=.), (<-.), (/<-.), (||.)
diff --git a/src/Database/Esqueleto/Internal/Sql.hs b/src/Database/Esqueleto/Internal/Sql.hs
--- a/src/Database/Esqueleto/Internal/Sql.hs
+++ b/src/Database/Esqueleto/Internal/Sql.hs
@@ -51,17 +51,16 @@
   , veryUnsafeCoerceSqlExprValueList
   ) where
 
-import Control.Applicative (Applicative(..), (<$>), (<$))
 import Control.Arrow ((***), first)
 import Control.Exception (throw, throwIO)
-import Control.Monad (ap, MonadPlus(..), liftM)
+import Control.Monad (ap, MonadPlus(..), join, void)
 import Control.Monad.IO.Class (MonadIO(..))
 import Control.Monad.Trans.Class (lift)
 import Control.Monad.Trans.Resource (MonadResource)
 import Data.Acquire (with, allocateAcquire, Acquire)
 import Data.Int (Int64)
 import Data.List (intersperse)
-import Data.Monoid (Last(..), Monoid(..), (<>))
+import Data.Monoid (Last(..), (<>))
 import Data.Proxy (Proxy(..))
 import Database.Esqueleto.Internal.PersistentImport
 import Database.Persist.Sql.Util (entityColumnNames, entityColumnCount, parseEntityValues, isIdField, hasCompositeKey)
@@ -648,7 +647,7 @@
 
     deconstruct :: (TLB.Builder, [PersistValue]) -> ([TLB.Builder], [PersistValue])
     deconstruct ("?", [PersistList vals]) = (replicate (length vals) "?", vals)
-    deconstruct (b, []) = (TLB.fromLazyText <$> TL.splitOn "," (TLB.toLazyText b), [])
+    deconstruct (b', []) = (TLB.fromLazyText <$> TL.splitOn "," (TLB.toLazyText b'), [])
     deconstruct x = err $ "cannot deconstruct " ++ show x ++ "."
 
     compose f1 f2 info
@@ -667,7 +666,7 @@
 -- | (Internal) A raw SQL value.  The same warning from
 -- 'unsafeSqlBinOp' applies to this function as well.
 unsafeSqlValue :: TLB.Builder -> SqlExpr (Value a)
-unsafeSqlValue v = ERaw Never $ \_ -> (v, mempty)
+unsafeSqlValue v = ERaw Never $ const (v, mempty)
 {-# INLINE unsafeSqlValue #-}
 
 
@@ -784,12 +783,9 @@
                 , MonadResource m )
              => SqlQuery a
              -> C.Source (SqlPersistT m) r
-selectSource query = do
-    src <- lift $ do
-        res <- rawSelectSource SELECT query
-        fmap snd $ allocateAcquire res
-    src
-
+selectSource query = join . lift $ do
+  res <- rawSelectSource SELECT query
+  snd <$> allocateAcquire res
 
 -- | Execute an @esqueleto@ @SELECT@ query inside @persistent@'s
 -- 'SqlPersistT' monad and return a list of rows.
@@ -910,8 +906,7 @@
 delete :: ( MonadIO m )
        => SqlQuery ()
        -> SqlWriteT m ()
-delete = liftM (const ()) . deleteCount
-
+delete = void . deleteCount
 
 -- | Same as 'delete', but returns the number of rows affected.
 deleteCount :: ( MonadIO m )
@@ -936,8 +931,7 @@
           , SqlEntity val )
        => (SqlExpr (Entity val) -> SqlQuery ())
        -> SqlWriteT m ()
-update = liftM (const ()) . updateCount
-
+update = void . updateCount
 
 -- | Same as 'update', but returns the number of rows affected.
 updateCount :: ( MonadIO m
@@ -1037,7 +1031,7 @@
         DistinctOn exprs -> first (("SELECT DISTINCT ON (" <>) . (<> ") ")) $
                             uncommas' (processExpr <$> exprs)
       where processExpr (EDistinctOn f) = materializeExpr info f
-    withCols v = v <> (sqlSelectCols info ret)
+    withCols v = v <> sqlSelectCols info ret
     plain    v = (v, [])
 
 
@@ -1122,7 +1116,7 @@
       let fs = f info
           vals = repeat []
       in zip (map (<> orderByType t) fs) vals
-    mk EOrderRandom = [first ((<> "RANDOM()")) mempty]
+    mk EOrderRandom = [first (<> "RANDOM()") mempty]
     orderByType ASC  = " ASC"
     orderByType DESC = " DESC"
 
@@ -1215,8 +1209,7 @@
               in (process ed, mempty)
   sqlSelectColCount = entityColumnCount . entityDef . getEntityVal
   sqlSelectProcessRow = parseEntityValues ed
-    where ed = entityDef $ getEntityVal $ (Proxy :: Proxy (SqlExpr (Entity a)))
-
+    where ed = entityDef $ getEntityVal (Proxy :: Proxy (SqlExpr (Entity a)))
 
 getEntityVal :: Proxy (SqlExpr (Entity a)) -> Proxy a
 getEntityVal = const Proxy
@@ -1749,7 +1742,7 @@
 -- /Since: 2.4.2/
 insertSelect :: (MonadIO m, PersistEntity a) =>
   SqlQuery (SqlExpr (Insertion a)) -> SqlWriteT m ()
-insertSelect = liftM (const ()) . insertSelectCount
+insertSelect = void . insertSelectCount
 
 -- | Insert a 'PersistField' for every selected value, return the count afterward
 insertSelectCount :: (MonadIO m, PersistEntity a) =>
diff --git a/test/Test.hs b/test/Test.hs
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -18,18 +18,13 @@
  #-}
 module Main (main) where
 
-import Control.Applicative ((<$>))
-import Control.Arrow ((&&&))
-import Control.Exception (IOException)
 import Control.Monad (forM_, replicateM, replicateM_, void)
 import Control.Monad.IO.Class (MonadIO(liftIO))
 import Control.Monad.Logger (MonadLogger(..), runStderrLoggingT, runNoLoggingT)
 import Control.Monad.Trans.Control (MonadBaseControl(..))
 import Control.Monad.Trans.Reader (ReaderT)
 import Data.Char (toLower, toUpper)
-import Data.List (sortBy)
 import Data.Monoid ((<>))
-import Data.Ord (comparing)
 import Database.Esqueleto
 #if   defined (WITH_POSTGRESQL)
 import Database.Persist.Postgresql (withPostgresqlConn)
@@ -53,7 +48,6 @@
 import qualified Data.List as L
 import qualified Data.Set as S
 import qualified Data.Text.Lazy.Builder as TLB
-import qualified Database.Esqueleto.PostgreSQL as EP
 import qualified Database.Esqueleto.Internal.Sql as EI
 
 
@@ -154,7 +148,7 @@
 
       it "works for a single NULL value" $
         run $ do
-          ret <- select $ return $ nothing
+          ret <- select $ return nothing
           liftIO $ ret `shouldBe` [ Value (Nothing :: Maybe Int) ]
 
     describe "select/from" $ do
@@ -289,7 +283,7 @@
               number = 101
               Right thePk = keyFromValues [toPersistValue number]
           fcPk <- insert fc
-          [Entity _ ret] <- select $ from $ return
+          [Entity _ ret] <- select $ from return
           liftIO $ do
             ret `shouldBe` fc
             fcPk `shouldBe` thePk