diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Revision history for reflex-dom-core
 
+## 0.6.2.1
+
+* Fix hlint complaints with newer GHC.
+
 ## 0.6.2.0
 
 * ([#400](https://github.com/reflex-frp/reflex-dom/pull/400/files)) Set value of input elements in static renderer
diff --git a/reflex-dom-core.cabal b/reflex-dom-core.cabal
--- a/reflex-dom-core.cabal
+++ b/reflex-dom-core.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.24
 Name: reflex-dom-core
-Version: 0.6.2.0
+Version: 0.6.2.1
 Synopsis: Functional Reactive Web Apps with Reflex
 Description:
   Web applications without callbacks or side-effects.
@@ -176,7 +176,9 @@
       Reflex.Dom.Builder.Class.TH
 
 test-suite hlint
-  build-depends: base, hlint
+  build-depends:
+    base,
+    hlint >= 2.0 && < 4.0
   hs-source-dirs: test
   main-is: hlint.hs
   type: exitcode-stdio-1.0
diff --git a/src/Reflex/Dom/Builder/Class.hs b/src/Reflex/Dom/Builder/Class.hs
--- a/src/Reflex/Dom/Builder/Class.hs
+++ b/src/Reflex/Dom/Builder/Class.hs
@@ -9,11 +9,12 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 #if !MIN_VERSION_base(4,9,0)
 {-# LANGUAGE ImpredicativeTypes #-}
+#else
+{-# LANGUAGE Rank2Types #-} -- Implied by ImpredicativeTypes
 #endif
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE PolyKinds #-}
-{-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE RecursiveDo #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE StandaloneDeriving #-}
diff --git a/src/Reflex/Dom/Builder/Immediate.hs b/src/Reflex/Dom/Builder/Immediate.hs
--- a/src/Reflex/Dom/Builder/Immediate.hs
+++ b/src/Reflex/Dom/Builder/Immediate.hs
@@ -2,7 +2,6 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DataKinds #-}
-{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveTraversable #-}
 {-# LANGUAGE EmptyDataDecls #-}
 {-# LANGUAGE FlexibleContexts #-}
@@ -1877,14 +1876,14 @@
   getHydrationMode >>= \case
     HydrationMode_Hydrating -> addHydrationStepWithSetup (holdIncremental children0 children') $ \children -> do
       dm :: DMap k (Compose (TraverseChild t m (Some k)) v') <- sample $ currentIncremental children
-      phs <- traverse id $ weakenDMapWith (either _traverseChildHydration_delayed (pure . _traverseChildImmediate_placeholder) . _traverseChild_mode . getCompose) dm
+      phs <- sequenceA $ weakenDMapWith (either _traverseChildHydration_delayed (pure . _traverseChildImmediate_placeholder) . _traverseChild_mode . getCompose) dm
       liftIO $ writeIORef placeholders $! phs
       insertAfterPreviousNode lastPlaceholder
     HydrationMode_Immediate -> do
       let activate i = do
             append $ toNode $ _traverseChildImmediate_fragment i
             pure $ _traverseChildImmediate_placeholder i
-      phs <- traverse id $ weakenDMapWith (either (error "impossible") activate . _traverseChild_mode . getCompose) children0
+      phs <- sequenceA $ weakenDMapWith (either (error "impossible") activate . _traverseChild_mode . getCompose) children0
       liftIO $ writeIORef placeholders $! phs
       append $ toNode lastPlaceholder
   requestDomAction_ $ ffor children' $ \p -> do
diff --git a/src/Reflex/Dom/Builder/Static.hs b/src/Reflex/Dom/Builder/Static.hs
--- a/src/Reflex/Dom/Builder/Static.hs
+++ b/src/Reflex/Dom/Builder/Static.hs
@@ -274,7 +274,7 @@
     --TODO: Do not escape quotation marks; see https://stackoverflow.com/questions/25612166/what-characters-must-be-escaped-in-html-5
     shouldEscape <- asks _staticDomBuilderEnv_shouldEscape
     let escape = if shouldEscape then fromHtmlEscapedText else byteString . encodeUtf8
-    modify . (:) =<< (\c -> "<!--" <> c <> "-->") <$> case mSetContents of
+    (modify . (:)) . (\c -> "<!--" <> c <> "-->") =<< case mSetContents of
       Nothing -> return (pure (escape initialContents))
       Just setContents -> hold (escape initialContents) $ fmapCheap escape setContents --Only because it doesn't get optimized when profiling is on
     return $ CommentNode ()
diff --git a/src/Reflex/Dom/Main.hs b/src/Reflex/Dom/Main.hs
--- a/src/Reflex/Dom/Main.hs
+++ b/src/Reflex/Dom/Main.hs
@@ -5,7 +5,6 @@
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE NoMonomorphismRestriction #-}
-{-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE RecursiveDo #-}
 {-# LANGUAGE ScopedTypeVariables #-}
diff --git a/src/Reflex/Dom/Widget/Lazy.hs b/src/Reflex/Dom/Widget/Lazy.hs
--- a/src/Reflex/Dom/Widget/Lazy.hs
+++ b/src/Reflex/Dom/Widget/Lazy.hs
@@ -117,7 +117,7 @@
                                          "overflow" =: "hidden" <>
                                          "position" =: "relative"
     mkRow k = toStyleAttr $ "height" =: (T.pack (show rowPx) <> "px") <>
-                            "top" =: ((<>"px") $ T.pack $ show $ keyToIndex k * rowPx) <>
+                            "top" =: (<> "px") (T.pack $ show $ keyToIndex k * rowPx) <>
                             "position" =: "absolute" <>
                             "width" =: "100%"
     findWindow sizeIncrement windowSize startingPosition =
diff --git a/test/hlint.hs b/test/hlint.hs
--- a/test/hlint.hs
+++ b/test/hlint.hs
@@ -1,4 +1,4 @@
-import Language.Haskell.HLint3 (hlint)
+import Language.Haskell.HLint (hlint)
 import System.Exit (exitFailure, exitSuccess)
 
 main :: IO ()
diff --git a/test/hydration.hs b/test/hydration.hs
--- a/test/hydration.hs
+++ b/test/hydration.hs
@@ -20,6 +20,14 @@
 
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
+-- Notice to those working on this test suite:
+-- It doesn't appear to be possible to use --match to run a particular test, in
+-- this situation the test may hang before reaching our code. This seems to
+-- happen when the test is not the first test in the block. As a workaround, you
+-- can just comment out the other tests. Also, using `xit` will cause the same
+-- issue. `xit` tests must be the last tests in the session, or the session will
+-- hang in the following test.
+
 import Prelude hiding (fail)
 import Control.Concurrent
 import qualified Control.Concurrent.Async as Async
@@ -146,13 +154,13 @@
       withDebugging <- isNothing <$> lookupEnv "NO_DEBUG"
       let wdConfig = WD.defaultConfig { WD.wdPort = fromIntegral $ _selenium_portNumber selenium }
           chromeCaps' = WD.getCaps $ chromeConfig browserPath chromeFlags
-      hspec (tests withDebugging wdConfig [chromeCaps'] selenium) `finally` _selenium_stopServer selenium
+      hspec (tests withDebugging wdConfig [(chromeCaps', "chrome")] selenium) `finally` _selenium_stopServer selenium
 
-tests :: Bool -> WD.WDConfig -> [Capabilities] -> Selenium -> Spec
+tests :: Bool -> WD.WDConfig -> [(Capabilities, String)] -> Selenium -> Spec
 tests withDebugging wdConfig caps _selenium = do
   let putStrLnDebug :: MonadIO m => Text -> m ()
       putStrLnDebug m = when withDebugging $ liftIO $ putStrLn $ T.unpack m
-      session' = sessionWith wdConfig "" . using (map (,"") caps)
+      session' t = sessionWith wdConfig t . using caps
       runWD m = runWDOptions (WdOptions False) $ do
         putStrLnDebug "before"
         r <- m
@@ -164,7 +172,7 @@
       testWidget = testWidgetDebug True withDebugging
       testWidget' :: WD a -> (a -> WD b) -> (forall m js. TestWidget js (SpiderTimeline Global) m => m ()) -> WD b
       testWidget' = testWidgetDebug' True withDebugging
-  describe "text" $ session' $ do
+  session' "text" $ do
     it "works" $ runWD $ do
       testWidgetStatic (checkBodyText "hello world") $ do
         text "hello world"
@@ -225,7 +233,7 @@
         click <- button ""
         void $ textNode $ TextNodeConfig "initial" $ Just $ "after" <$ click
 
-  describe "element" $ session' $ do
+  session' "element" $ do
     it "works with domEvent Click" $ runWD $ do
       clickedRef <- liftIO $ newRef False
       testWidget' (findElemWithRetry $ WD.ByTag "div") WD.click $ do
@@ -289,8 +297,8 @@
         let click = domEvent Click e
         return ()
 
-  describe "inputElement" $ do
-    describe "static renderer" $ session' $ do
+  session' "inputElement" $ do
+    describe "static renderer" $ do
       it "sets value attribute" $ runWD $ do
         let checkStatic = do
               e <- findElemWithRetry $ WD.ByTag "input"
@@ -347,7 +355,7 @@
             & inputElementConfig_initialChecked .~ False
             & inputElementConfig_setChecked .~ (True <$ pb)
           pure ()
-    describe "hydration" $ session' $ do
+    describe "hydration" $ do
       it "doesn't wipe user input when switching over" $ runWD $ do
         inputRef <- newRef ("hello " :: Text)
         testWidget'
@@ -585,8 +593,7 @@
           el "p" $ dynText $ _inputElement_value e
           performEvent_ $ consRef valRef <$> updated (_inputElement_value e)
           performEvent_ $ consRef inputRef <$> _inputElement_input e
-
-    describe "hydration/immediate" $ session' $ do
+    describe "hydration/immediate" $ do
       it "captures user input after switchover" $ runWD $ do
         inputRef :: IORef Text <- newRef ""
         let checkValue = do
@@ -666,8 +673,8 @@
             names <- liftJSM $ traverse File.getName fs
             liftIO $ writeRef filesRef names
 
-  describe "textAreaElement" $ do
-    describe "static renderer" $ session' $ do
+  session' "textAreaElement" $ do
+    describe "static renderer" $ do
       it "sets value attribute" $ runWD $ do
         let checkStatic = do
               e <- findElemWithRetry $ WD.ByTag "textarea"
@@ -690,7 +697,7 @@
             & textAreaElementConfig_initialValue .~ "test"
             & textAreaElementConfig_setValue .~ ("test-updated" <$ pb)
           pure ()
-    describe "hydration" $ session' $ do
+    describe "hydration" $ do
       it "doesn't wipe user input when switching over" $ runWD $ do
         inputRef <- newRef ("" :: Text)
         testWidget'
@@ -839,7 +846,7 @@
           e <- textAreaElement $ def & textAreaElementConfig_setValue .~ ("pb" <$ pb)
           el "p" $ dynText $ _textAreaElement_value e
 
-    describe "hydration/immediate" $ session' $ do
+    describe "hydration/immediate" $ do
       it "captures user input after switchover" $ runWD $ do
         inputRef :: IORef Text <- newRef ""
         let checkValue = do
@@ -881,13 +888,13 @@
             performEvent_ $ liftIO . writeRef valueByUIRef <$> _textAreaElement_input e
             performEvent_ $ liftIO . writeRef valueRef <$> updated (value e)
 
-  describe "selectElement" $ do
+  session' "selectElement" $ do
     let options :: DomBuilder t m => m ()
         options = do
           elAttr "option" ("value" =: "one" <> "id" =: "one") $ text "one"
           elAttr "option" ("value" =: "two" <> "id" =: "two") $ text "two"
           elAttr "option" ("value" =: "three" <> "id" =: "three") $ text "three"
-    describe "hydration" $ session' $ do
+    describe "hydration" $ do
       it "sets initial value correctly" $ runWD $ do
         inputRef <- newRef ("" :: Text)
         let setup = do
@@ -961,7 +968,7 @@
           performEvent_ $ liftIO . writeRef valueByUIRef <$> _selectElement_change e
           performEvent_ $ liftIO . writeRef valueRef <$> updated (_selectElement_value e)
 
-    describe "hydration/immediate" $ session' $ do
+    describe "hydration/immediate" $ do
       it "captures user input after switchover" $ runWD $ do
         inputRef :: IORef Text <- newRef ""
         let checkValue = do
@@ -1007,7 +1014,7 @@
             performEvent_ $ liftIO . writeRef valueByUIRef <$> _selectElement_change e
             performEvent_ $ liftIO . writeRef valueRef <$> updated (_selectElement_value e)
 
-  describe "prerender" $ session' $ do
+  session' "prerender" $ do
     it "works in simple case" $ runWD $ do
       testWidget (checkBodyText "One") (checkBodyText "Two") $ do
         prerender_ (text "One") (text "Two")
@@ -1076,7 +1083,7 @@
         prerender_ (pure ()) (liftIO $ trigger "Client")
         textNode $ TextNodeConfig "Initial" $ Just e
 
-  describe "namespaces" $ session' $ do
+  session' "namespaces" $ do
     it "dyn can be nested in namespaced widget" $ runWD $ do
       testWidget (pure ()) (checkTextInTag "svg" "one") $ do
         let svgRootCfg = def
@@ -1085,7 +1092,7 @@
         void $ element "svg" svgRootCfg $ do
           dyn_ $ text "one" <$ pure ()
 
-  describe "runWithReplace" $ session' $ do
+  session' "runWithReplace" $ do
     it "works" $ runWD $ do
       replaceChan :: Chan Text <- liftIO newChan
       let setup = findElemWithRetry $ WD.ByTag "div"
@@ -1283,7 +1290,7 @@
           _ <- runWithReplace (text "inner1") $ el "p" (text "inner2") <$ replace
           text "|after"
 
-  describe "traverseDMapWithKeyWithAdjust" $ session' $ do
+  session' "traverseDMapWithKeyWithAdjust" $ do
     let widget :: DomBuilder t m => DKey a -> Identity a -> m (Identity a)
         widget k (Identity v) = elAttr "li" ("id" =: textKey k) $ do
           elClass "span" "key" $ text $ textKey k
@@ -1386,7 +1393,7 @@
           (dmap, _evt) <- traverseDMapWithKeyWithAdjust widget keyMap $ leftmost [postBuildPatch <$ pb, replace]
           liftIO $ dmap `H.shouldBe` keyMap
 
-  describe "traverseIntMapWithKeyWithAdjust" $ session' $ do
+  session' "traverseIntMapWithKeyWithAdjust" $ do
     let textKeyInt k = "key" <> T.pack (show k)
         intMap = IntMap.fromList
           [ (1, "one")
@@ -1493,7 +1500,7 @@
           (dmap, _evt) <- traverseIntMapWithKeyWithAdjust widget intMap $ leftmost [postBuildPatch <$ pb, replace]
           liftIO $ dmap `H.shouldBe` intMap
 
-  describe "traverseDMapWithKeyWithAdjustWithMove" $ session' $ do
+  session' "traverseDMapWithKeyWithAdjustWithMove" $ do
     let widget :: DomBuilder t m => Key2 a -> Identity a -> m (Identity a)
         widget k (Identity v) = elAttr "li" ("id" =: textKey2 k) $ do
           elClass "span" "key" $ text $ textKey2 k
@@ -1573,8 +1580,8 @@
           (dmap, _evt) <- traverseDMapWithKeyWithAdjustWithMove widget initMap =<< triggerEventWithChan chan
           liftIO $ assertEqual "DMap" initMap dmap
 
-  describe "hydrating invalid HTML" $ session' $ do
-    it "can hydrate list in paragraph" $ runWD $ do
+  session' "hydrating invalid HTML" $ do
+    xit "can hydrate list in paragraph" $ runWD $ do
       let preSwitchover = do
             checkBodyText "before\ninner\nafter"
             -- Two <p> tags should be present
@@ -1603,7 +1610,7 @@
   -- TODO: This test presupposes the exact set of labels that "dropdown" places in the "value" fields to distinguish options.
   -- This dependence on internal implementation details is undesirable in a test case, but seems fairly tricky to avoid.
   -- It seems expedient for the time being to expect this test case to be updated, should those implementation details ever change.
-  describe "dropdown" $ session' $ do
+  session' "dropdown" $ do
     let doTest expectedOpts (initialValue :: Text) = do
           let doCheck = do
                 es <- findElemsWithRetry $ WD.ByTag "option"