diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,3 +24,7 @@
 
 * Second version. Added the module Case.Hashable.Cuckoo variant based on the Hashtable (cuckoo hash) usage. 
 Added the respective dependency. 
+
+## 0.2.1.0 -- 2021-10-30
+
+* Second version revised A. Discontinued the base < 4.9 versions. 
diff --git a/mmsyn2-array.cabal b/mmsyn2-array.cabal
--- a/mmsyn2-array.cabal
+++ b/mmsyn2-array.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                mmsyn2-array
-version:             0.2.0.0
+version:             0.2.1.0
 synopsis:            A library that can be used for multiple Ord a => a -> b transformations.
 description:         A library that can be used as a @case ... of@ construction replacement for various cases. Since the 0.2.0.0 version also uses the cuckoo hashtables in the respective module.
 homepage:            https://hackage.haskell.org/package/mmsyn2-array
@@ -21,6 +21,6 @@
   -- other-modules:
   other-extensions:    UnboxedTuples, BangPatterns, FlexibleContexts, MagicHash
   ghc-options:         -funbox-strict-fields
-  build-depends:       base >=4.8 && <5, hashtables >=1.2.3 && <2, hashable >= 1.2.7 && <2, ghc-prim >=0.4 && <1
+  build-depends:       base >=4.9 && <5, hashtables >=1.2.3 && <2, hashable >= 1.2.7 && <2, ghc-prim >=0.5 && <1
   -- hs-source-dirs:
   default-language:    Haskell2010