diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -5,6 +5,12 @@
 ## Unreleased changes
 
 
+## 0.4.0.1
+
+-   Minor changes mostly related to tooling.
+-   Nix support.
+
+
 ## 0.4.0.0
 
 -   Do not export data constructors nor record fields.
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright Dominik Schrempf (c) 2020
+Copyright Dominik Schrempf (c) 2021
 
 All rights reserved.
 
diff --git a/bench/Bench.hs b/bench/Bench.hs
--- a/bench/Bench.hs
+++ b/bench/Bench.hs
@@ -1,7 +1,7 @@
 -- |
 -- Module      :  Main
 -- Description :  Benchmark circular stacks
--- Copyright   :  (c) Dominik Schrempf, 2020
+-- Copyright   :  (c) Dominik Schrempf, 2021
 -- License     :  GPL-3.0-or-later
 --
 -- Maintainer  :  dominik.schrempf@gmail.com
diff --git a/circular.cabal b/circular.cabal
--- a/circular.cabal
+++ b/circular.cabal
@@ -1,6 +1,6 @@
-cabal-version:  1.12
+cabal-version:  2.0
 name:           circular
-version:        0.4.0.0
+version:        0.4.0.1
 synopsis:       Circular fixed-sized mutable vectors
 description:    Please see the README at <https://github.com/dschrempf/circular#readme>
 category:       Math, Data Structures
@@ -8,7 +8,7 @@
 bug-reports:    https://github.com/dschrempf/circular/issues
 author:         Dominik Schrempf
 maintainer:     dominik.schrempf@gmail.com
-copyright:      Dominik Schrempf (2020)
+copyright:      Dominik Schrempf (2021)
 license:        BSD3
 license-file:   LICENSE
 build-type:     Simple
@@ -40,6 +40,8 @@
   other-modules:
       Data.Stack.CircularSpec
       Paths_circular
+  autogen-modules:
+      Paths_circular
   hs-source-dirs: test
   ghc-options: -Wall -Wunused-packages
   build-depends:
@@ -57,6 +59,8 @@
   type: exitcode-stdio-1.0
   main-is: Bench.hs
   other-modules:
+      Paths_circular
+  autogen-modules:
       Paths_circular
   hs-source-dirs: bench
   ghc-options: -Wall -Wunused-packages
diff --git a/src/Data/Stack/Circular.hs b/src/Data/Stack/Circular.hs
--- a/src/Data/Stack/Circular.hs
+++ b/src/Data/Stack/Circular.hs
@@ -7,7 +7,7 @@
 -- |
 -- Module      :  Data.Stack.Circular
 -- Description :  Circular stacks of fixed size
--- Copyright   :  (c) 2020 Dominik Schrempf
+-- Copyright   :  (c) 2021 Dominik Schrempf
 -- License     :  GPL-3.0-or-later
 --
 -- Maintainer  :  dominik.schrempf@gmail.com
@@ -250,6 +250,11 @@
   }
   deriving (Eq, Read, Show)
 
+-- This (per se useless) top level splice separates the module into two
+-- declaration groups. This is required, because the expression slices below
+-- (which are now in the second declaration group) can only refer to definitions
+-- outside their own declaration group. See
+-- https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/template_haskell.html.
 $(return [])
 
 instance (FromJSON (v a)) => FromJSON (Stack v a) where
diff --git a/test/Data/Stack/CircularSpec.hs b/test/Data/Stack/CircularSpec.hs
--- a/test/Data/Stack/CircularSpec.hs
+++ b/test/Data/Stack/CircularSpec.hs
@@ -5,7 +5,7 @@
 -- |
 --   Module      :  Data.Stack.CircularSpec
 --   Description :  Unit tests for Data.Stack.Circular
---   Copyright   :  (c) Dominik Schrempf, 2020
+--   Copyright   :  (c) Dominik Schrempf, 2021
 --   License     :  GPL-3.0-or-later
 --
 --   Maintainer  :  dominik.schrempf@gmail.com