diff --git a/.hlint.yaml b/.hlint.yaml
--- a/.hlint.yaml
+++ b/.hlint.yaml
@@ -1,3 +1,5 @@
+- arguments: [-XCPP]
+
 - ignore: {name: Use fmap}
 - ignore: {name: Avoid lambda}
 - ignore: {name: Redundant lambda}
diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+1.21.9 [2022.05.18]
+-------------------
+* Allow building with `transformers-0.6.*`.
+
 1.21.8 [2021.11.15]
 -------------------
 * Allow building with `hashable-1.4.*`.
diff --git a/linear.cabal b/linear.cabal
--- a/linear.cabal
+++ b/linear.cabal
@@ -1,6 +1,6 @@
 name:          linear
 category:      Math, Algebra
-version:       1.21.8
+version:       1.21.9
 license:       BSD3
 cabal-version: >= 1.10
 license-file:  LICENSE
@@ -19,8 +19,8 @@
              , GHC == 8.6.5
              , GHC == 8.8.4
              , GHC == 8.10.7
-             , GHC == 9.0.1
-             , GHC == 9.2.1
+             , GHC == 9.0.2
+             , GHC == 9.2.2
 extra-source-files:
   .gitignore
   .hlint.yaml
@@ -65,7 +65,7 @@
     semigroups           >= 0.9   && < 1,
     semigroupoids        >= 5.2.1 && < 6,
     tagged               >= 0.8.6 && < 1,
-    transformers         >= 0.5   && < 0.6,
+    transformers         >= 0.5   && < 0.7,
     transformers-compat  >= 0.5.0.4 && < 1,
     unordered-containers >= 0.2.3 && < 0.3,
     vector               >= 0.12.1.2 && < 0.13,
diff --git a/src/Linear/Affine.hs b/src/Linear/Affine.hs
--- a/src/Linear/Affine.hs
+++ b/src/Linear/Affine.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE DeriveGeneric #-}
diff --git a/src/Linear/Matrix.hs b/src/Linear/Matrix.hs
--- a/src/Linear/Matrix.hs
+++ b/src/Linear/Matrix.hs
@@ -4,6 +4,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
 
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