diff --git a/src/UniqueLogic/ST/Example/Verify.hs b/src/UniqueLogic/ST/Example/Verify.hs
--- a/src/UniqueLogic/ST/Example/Verify.hs
+++ b/src/UniqueLogic/ST/Example/Verify.hs
@@ -59,7 +59,6 @@
    (<*>) = ap
 
 instance (Monad m) => Monad (Track m) where
-   return = pure
    x >>= k  =  Track $ UMT.bind (runTrack x) (runTrack . k)
 
 
diff --git a/src/UniqueLogic/ST/MonadTrans.hs b/src/UniqueLogic/ST/MonadTrans.hs
--- a/src/UniqueLogic/ST/MonadTrans.hs
+++ b/src/UniqueLogic/ST/MonadTrans.hs
@@ -64,5 +64,4 @@
    (<*>) = ap
 
 instance (C t, Monad m) => Monad (Wrap t m) where
-   return = pure
    x >>= k  =  wrap $ bind (unwrap x) (unwrap . k)
diff --git a/src/UniqueLogic/ST/System.hs b/src/UniqueLogic/ST/System.hs
--- a/src/UniqueLogic/ST/System.hs
+++ b/src/UniqueLogic/ST/System.hs
@@ -73,7 +73,6 @@
    (<*>) = ap
 
 instance Monad (T w s) where
-   return = pure
    Cons x >>= k  = Cons $ run . k =<< x
 
 
diff --git a/src/UniqueLogic/ST/Test.hs b/src/UniqueLogic/ST/Test.hs
--- a/src/UniqueLogic/ST/Test.hs
+++ b/src/UniqueLogic/ST/Test.hs
@@ -10,7 +10,7 @@
 import Control.Monad.Trans.Identity (IdentityT, )
 import Control.Monad.ST (ST, runST, )
 import Control.Monad (join, liftM2, )
-import Data.Monoid (Monoid(mempty, mappend))
+import Data.Monoid (Monoid(mempty))
 import Data.Semigroup (Semigroup((<>)), )
 
 import Data.List (sortBy, )
@@ -32,7 +32,6 @@
 
 instance Monoid (Check s) where
    mempty = Check $ return True
-   mappend = (<>)
 
 {-
 Take a system of six equations and seven variables
diff --git a/unique-logic.cabal b/unique-logic.cabal
--- a/unique-logic.cabal
+++ b/unique-logic.cabal
@@ -1,6 +1,6 @@
 Cabal-Version:    2.2
 Name:             unique-logic
-Version:          0.4.1
+Version:          0.4.1.1
 License:          BSD-3-Clause
 License-File:     LICENSE
 Author:           Henning Thielemann
@@ -66,7 +66,7 @@
 Build-Type:        Simple
 
 Source-Repository this
-  Tag:         0.4.1
+  Tag:         0.4.1.1
   Type:        darcs
   Location:    https://hub.darcs.net/thielema/unique-logic/
 
@@ -79,7 +79,7 @@
     explicit-exception >=0.1.7 && <0.3,
     transformers >=0.2 && <0.7,
     utility-ht >=0.0.9 && <0.1,
-    base >= 4 && <5
+    base >=4.11 && <5
   GHC-Options:      -Wall
   Default-Language: Haskell98
   Hs-Source-Dirs:   src