diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,8 @@
 # mixed-types-num change log
 
+* v 0.5.12 2023-08-14
+  * compatible with ghc 9.6.2
+  * remove dependency on mtl
 * v 0.5.11 2022-08-25
   * left-first and/or for CE/CN monad
 * v 0.5.10 2022-07-13
diff --git a/mixed-types-num.cabal b/mixed-types-num.cabal
--- a/mixed-types-num.cabal
+++ b/mixed-types-num.cabal
@@ -1,11 +1,11 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.4.
+-- This file has been generated from package.yaml by hpack version 0.35.2.
 --
 -- see: https://github.com/sol/hpack
 
 name:           mixed-types-num
-version:        0.5.11
+version:        0.5.12
 synopsis:       Alternative Prelude with numeric and logic expressions typed bottom-up
 description:    Please see the README on GitHub at <https://github.com/michalkonecny/mixed-types-num#readme>
 category:       Math
@@ -13,7 +13,7 @@
 bug-reports:    https://github.com/michalkonecny/mixed-types-num/issues
 author:         Michal Konecny
 maintainer:     mikkonecny@gmail.com
-copyright:      2015-2021 Michal Konecny
+copyright:      2015-2023 Michal Konecny
 license:        BSD3
 license-file:   LICENSE
 build-type:     Simple
@@ -74,7 +74,6 @@
     , collect-errors >=0.1.1
     , hspec >=2.1
     , hspec-smallcheck >=0.3
-    , mtl
     , smallcheck >=1.1
     , template-haskell
   default-language: Haskell2010
diff --git a/src/Data/Convertible/Base.hs b/src/Data/Convertible/Base.hs
--- a/src/Data/Convertible/Base.hs
+++ b/src/Data/Convertible/Base.hs
@@ -36,7 +36,6 @@
                              )
 where
 import Prelude
-import Control.Monad.Error
 import Data.Typeable
 
 {- | The result of a safe conversion via 'safeConvert'. -}
@@ -96,9 +95,6 @@
       convDestType :: String,
       convErrorMessage :: String}
                     deriving (Eq, Read, Show)
-
-instance Error ConvertError where
-    strMsg x = ConvertError "(unknown)" "(unknown)" "(unknown)" x
 
 convError' :: (Show a, Typeable a, Typeable b) =>
                String -> a -> b -> ConvertResult b