diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+1.2.2
+-----
+* Relaxed upper version bound for `transformers`.
+
 1.2.1
 -----
 * Explicitly mark `Data.StateVar` as Safe (or Trustworthy for GHC before 7.10).
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,5 +1,5 @@
 Copyright (c) 2014-2015, Edward Kmett
-Copyright (c) 2009-2018, Sven Panne
+Copyright (c) 2009-2021, Sven Panne
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/StateVar.cabal b/StateVar.cabal
--- a/StateVar.cabal
+++ b/StateVar.cabal
@@ -1,12 +1,12 @@
 name: StateVar
-version: 1.2.1
+version: 1.2.2
 synopsis: State variables
 description:
   This package contains state variables, which are references in the IO monad,
   like IORefs or parts of the OpenGL state.
 homepage: https://github.com/haskell-opengl/StateVar
 bug-reports: https://github.com/haskell-opengl/StateVar/issues
-copyright: Copyright (C) 2014-2015 Edward A. Kmett, 2009-2018 Sven Panne
+copyright: Copyright (C) 2014-2015 Edward A. Kmett, 2009-2021 Sven Panne
 license: BSD3
 license-file: LICENSE
 author: Sven Panne and Edward Kmett
@@ -26,6 +26,8 @@
   GHC == 8.6.5
   GHC == 8.8.4
   GHC == 8.10.3
+  GHC == 8.10.4
+  GHC == 9.0.1
 cabal-version: >= 1.10
 extra-source-files:
   README.md
@@ -38,7 +40,7 @@
   build-depends:
     base         >= 4   && < 5,
     stm          >= 2.3.0.1 && < 2.6,
-    transformers >= 0.3 && < 0.6
+    transformers >= 0.3 && < 0.7
 
   default-language: Haskell2010
   other-extensions:
diff --git a/src/Data/StateVar.hs b/src/Data/StateVar.hs
--- a/src/Data/StateVar.hs
+++ b/src/Data/StateVar.hs
@@ -16,7 +16,7 @@
 --------------------------------------------------------------------------------
 -- |
 -- Module      :  Data.StateVar
--- Copyright   :  (c) Edward Kmett 2014-2019, Sven Panne 2009-2018
+-- Copyright   :  (c) Edward Kmett 2014-2019, Sven Panne 2009-2021
 -- License     :  BSD3
 -- 
 -- Maintainer  :  Sven Panne <svenpanne@gmail.com>
