diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Changelog for moss
 
+## 0.2.0.1
+
+- Compatibility with `mtl-2.3` and above ([#3](https://github.com/mbg/moss/issues/3))
+
 ## 0.2
 
 - Add more languages supported by MOSS ([#2](https://github.com/mbg/moss/pull/2))
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -2,6 +2,7 @@
 
 ![GitHub](https://img.shields.io/github/license/mbg/moss)
 ![CI](https://github.com/mbg/moss/workflows/CI/badge.svg)
+![stackage-nightly](https://github.com/mbg/moss/workflows/stackage-nightly/badge.svg)
 [![Hackage](https://img.shields.io/hackage/v/moss)](https://hackage.haskell.org/package/moss)
 
 Haskell client library for [Moss](https://theory.stanford.edu/~aiken/moss/) which is an online service for checking for code similarity, primarily aimed at detecting plagiarism. 
diff --git a/moss.cabal b/moss.cabal
--- a/moss.cabal
+++ b/moss.cabal
@@ -1,21 +1,21 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.33.0.
+-- This file has been generated from package.yaml by hpack version 0.34.4.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: cdb107d0caf11126d5eefa6f4edb3750c1846dbd80ea9e7df483e783c4bbdac9
+-- hash: dd0e0eaf5949b0ee8286722bad8cd85ed2131c0b75e30cc22e343a96de6a5ce2
 
 name:           moss
-version:        0.2.0.0
+version:        0.2.0.1
 synopsis:       Haskell client for Moss
 description:    Please see the README on Github at <https://github.com/mbg/moss#readme>
 category:       Web
 homepage:       https://github.com/mbg/moss#readme
 bug-reports:    https://github.com/mbg/moss/issues
 author:         Michael B. Gale
-maintainer:     m.gale@warwick.ac.uk
-copyright:      Copyright (c) 2018 Michael B. Gale
+maintainer:     github@michael-gale.co.uk
+copyright:      Copyright (c) 2022 Michael B. Gale
 license:        MIT
 license-file:   LICENSE
 build-type:     Simple
@@ -30,7 +30,9 @@
 library
   hs-source-dirs:
       src
-  default-extensions: RecordWildCards OverloadedStrings
+  default-extensions:
+      RecordWildCards
+      OverloadedStrings
   build-depends:
       base >=4.7 && <5
     , bytestring
diff --git a/src/Stanford/Moss.hs b/src/Stanford/Moss.hs
--- a/src/Stanford/Moss.hs
+++ b/src/Stanford/Moss.hs
@@ -21,6 +21,7 @@
 --------------------------------------------------------------------------------
 
 import Control.Exception
+import Control.Monad
 import Control.Monad.State
 
 import Data.Monoid