diff --git a/battleship-combinatorics.cabal b/battleship-combinatorics.cabal
--- a/battleship-combinatorics.cabal
+++ b/battleship-combinatorics.cabal
@@ -1,5 +1,5 @@
 Name:             battleship-combinatorics
-Version:          0.0.1.1
+Version:          0.0.1.2
 License:          BSD3
 License-File:     LICENSE
 Author:           Henning Thielemann <haskell@henning-thielemann.de>
@@ -17,7 +17,7 @@
 Build-Type:       Simple
 
 Source-Repository this
-  Tag:         0.0.1.1
+  Tag:         0.0.1.2
   Type:        darcs
   Location:    https://hub.darcs.net/thielema/battleship-combinatorics/
 
@@ -44,7 +44,7 @@
     transformers >=0.3 && <0.7,
     utility-ht >=0.0.8 && <0.1,
     prelude-compat >=0.0 && <0.0.1,
-    base >=4.5 && <5
+    base >=4.11 && <5
 
   GHC-Options:      -Wall
   Hs-Source-Dirs:   src
diff --git a/src/Combinatorics/Battleship/Count/CountMap.hs b/src/Combinatorics/Battleship/Count/CountMap.hs
--- a/src/Combinatorics/Battleship/Count/CountMap.hs
+++ b/src/Combinatorics/Battleship/Count/CountMap.hs
@@ -270,5 +270,4 @@
 
 instance (Counter.C a, Storable a) => Monoid (T w a) where
    mempty = empty
-   mappend = merge
    mconcat = mergeMany
diff --git a/src/Combinatorics/Battleship/Fleet.hs b/src/Combinatorics/Battleship/Fleet.hs
--- a/src/Combinatorics/Battleship/Fleet.hs
+++ b/src/Combinatorics/Battleship/Fleet.hs
@@ -72,7 +72,6 @@
 
 instance Monoid T where
    mempty = Cons 0
-   mappend = (<>)
 
 instance Storable T where
    sizeOf = Store.sizeOf decons