diff --git a/reflex-dom-core/reflex-dom-core.cabal b/reflex-dom-core/reflex-dom-core.cabal
index 1590b1e..3285307 100644
--- a/reflex-dom-core/reflex-dom-core.cabal
+++ b/reflex-dom-core/reflex-dom-core.cabal
@@ -176,7 +176,9 @@ library
       Reflex.Dom.Builder.Class.TH
 
 test-suite hlint
-  build-depends: base, hlint
+  build-depends:
+    base,
+    hlint >= 3.0 && < 4.0
   hs-source-dirs: test
   main-is: hlint.hs
   type: exitcode-stdio-1.0
diff --git a/reflex-dom-core/src/Reflex/Dom/Builder/Class.hs b/reflex-dom-core/src/Reflex/Dom/Builder/Class.hs
index 3cb09b8..c791dfb 100644
--- a/reflex-dom-core/src/Reflex/Dom/Builder/Class.hs
+++ b/reflex-dom-core/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/reflex-dom-core/src/Reflex/Dom/Builder/Immediate.hs b/reflex-dom-core/src/Reflex/Dom/Builder/Immediate.hs
index af43167..40dbbd6 100644
--- a/reflex-dom-core/src/Reflex/Dom/Builder/Immediate.hs
+++ b/reflex-dom-core/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 @@ hoistTraverseWithKeyWithAdjust base mapPatch updateChildUnreadiness applyDomUpda
   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/reflex-dom-core/src/Reflex/Dom/Builder/Static.hs b/reflex-dom-core/src/Reflex/Dom/Builder/Static.hs
index c5ba4ce..140c25a 100644
--- a/reflex-dom-core/src/Reflex/Dom/Builder/Static.hs
+++ b/reflex-dom-core/src/Reflex/Dom/Builder/Static.hs
@@ -274,7 +274,7 @@ instance SupportsStaticDomBuilder t m => DomBuilder t (StaticDomBuilderT t m) wh
     --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/reflex-dom-core/src/Reflex/Dom/Main.hs b/reflex-dom-core/src/Reflex/Dom/Main.hs
index 54dab88..24219c7 100644
--- a/reflex-dom-core/src/Reflex/Dom/Main.hs
+++ b/reflex-dom-core/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/reflex-dom-core/src/Reflex/Dom/Widget/Lazy.hs b/reflex-dom-core/src/Reflex/Dom/Widget/Lazy.hs
index dabcdab..709bfe4 100644
--- a/reflex-dom-core/src/Reflex/Dom/Widget/Lazy.hs
+++ b/reflex-dom-core/src/Reflex/Dom/Widget/Lazy.hs
@@ -117,7 +117,7 @@ virtualList heightPx rowPx maxIndex i0 setI keyToIndex items0 itemsUpdate itemBu
                                          "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/reflex-dom-core/test/hlint.hs b/reflex-dom-core/test/hlint.hs
index a901d72..ae3f858 100644
--- a/reflex-dom-core/test/hlint.hs
+++ b/reflex-dom-core/test/hlint.hs
@@ -1,4 +1,4 @@
-import Language.Haskell.HLint3 (hlint)
+import Language.Haskell.HLint (hlint)
 import System.Exit (exitFailure, exitSuccess)
 
 main :: IO ()