diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,12 @@
 # NEXT
 
+# 0.4.2
+
+* Add `Functor` instance for `Unbound.Generics.LocallyNameless.Internal.Iso.Exchange`
+  Thanks to Emily Pillmore (emilypi)
+* Import `MonadPlus` and `MonadFix` explicitly when building with mtl-2.3
+* Builds with GHC 9.0, GHC 9.2
+
 # 0.4.1
 
 * Add `MonadFail` instances for `LFreshMT` and `FreshMT`
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,9 +1,11 @@
 # unbound-generics
 
 [![Join the chat at https://gitter.im/lambdageek/unbound-generics](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/lambdageek/unbound-generics?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![Discord](https://img.shields.io/discord/732650960471720076?logo=discord)](https://discord.gg/CRfu93W)
 
 [![Hackage](https://img.shields.io/hackage/v/unbound-generics.svg)](https://hackage.haskell.org/package/unbound-generics)
-[![Build Status](https://travis-ci.org/lambdageek/unbound-generics.svg)](https://travis-ci.org/lambdageek/unbound-generics)
+[![CI](https://github.com/lambdageek/unbound-generics/workflows/CI/badge.svg)](https://github.com/lambdageek/unbound-generics/actions?query=workflow%3ACI+branch%3Amaster)
+<!-- [![Build Status](https://travis-ci.org/lambdageek/unbound-generics.svg)](https://travis-ci.org/lambdageek/unbound-generics) -->
 
 Support for programming with names and binders using GHC Generics.
 
diff --git a/src/Unbound/Generics/LocallyNameless/Fresh.hs b/src/Unbound/Generics/LocallyNameless/Fresh.hs
--- a/src/Unbound/Generics/LocallyNameless/Fresh.hs
+++ b/src/Unbound/Generics/LocallyNameless/Fresh.hs
@@ -24,6 +24,10 @@
 #if MIN_VERSION_base(4,9,0)
 import qualified Control.Monad.Fail as Fail
 #endif
+#if MIN_VERSION_mtl(2,3,0)
+import Control.Monad (MonadPlus)
+import Control.Monad.Fix (MonadFix)
+#endif
 import Control.Monad.Trans
 import Control.Monad.Trans.Except
 import Control.Monad.Trans.Error
diff --git a/src/Unbound/Generics/LocallyNameless/Internal/Iso.hs b/src/Unbound/Generics/LocallyNameless/Internal/Iso.hs
--- a/src/Unbound/Generics/LocallyNameless/Internal/Iso.hs
+++ b/src/Unbound/Generics/LocallyNameless/Internal/Iso.hs
@@ -6,6 +6,9 @@
 
 data Exchange a b s t = Exchange (s -> a) (b -> t)
 
+instance Functor (Exchange a b s) where
+  fmap f (Exchange p q) = Exchange p (f . q)
+
 instance Profunctor (Exchange a b) where
   dimap f g (Exchange h k) = Exchange (h . f ) (g . k)
 
diff --git a/src/Unbound/Generics/LocallyNameless/LFresh.hs b/src/Unbound/Generics/LocallyNameless/LFresh.hs
--- a/src/Unbound/Generics/LocallyNameless/LFresh.hs
+++ b/src/Unbound/Generics/LocallyNameless/LFresh.hs
@@ -68,6 +68,10 @@
 #if MIN_VERSION_base(4,9,0)
 import qualified Control.Monad.Fail as Fail
 #endif
+#if MIN_VERSION_mtl(2,3,0)
+import Control.Monad (MonadPlus)
+import Control.Monad.Fix (MonadFix)
+#endif
 import Control.Monad.Reader
 import Control.Monad.Identity
 import Control.Applicative (Applicative, Alternative)
diff --git a/unbound-generics.cabal b/unbound-generics.cabal
--- a/unbound-generics.cabal
+++ b/unbound-generics.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                unbound-generics
-version:             0.4.1
+version:             0.4.2
 synopsis:            Support for programming with names and binders using GHC Generics
 description:         Specify the binding structure of your data type with an
                      expressive set of type combinators, and unbound-generics
@@ -22,14 +22,14 @@
 license-file:        LICENSE
 author:              Aleksey Kliger
 maintainer:          aleksey@lambdageek.org
-copyright:           (c) 2014-2020, Aleksey Kliger
+copyright:           (c) 2014-2022, Aleksey Kliger
 category:            Language
 build-type:          Simple
 extra-source-files:  examples/*.hs, examples/*.lhs,
                      README.md,
                      Changelog.md
 cabal-version:       >=1.10
-tested-with: GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.3, GHC == 8.10.*
+tested-with: GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.3, GHC == 8.10.*, GHC == 9.0.*, GHC == 9.2.*
              
 library
   exposed-modules:     Unbound.Generics.LocallyNameless