diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,10 @@
 
 * First version revised B. Fixed issue with the first and last elements of the array that were not taken into account.
 
-## 0.1.2.0 -- 2021-03-28
+## 0.1.2.0 -- 2021-03-29
 
 * First version revised C. Some code optimization improvements. Changed the inner implementation and imported modules.
+
+## 0.1.3.0 -- 2021-03-29
+
+* First version revised D. Fixed issues with being not compiled for GHC < 8.0* series. 
diff --git a/CaseBi/Arr.hs b/CaseBi/Arr.hs
--- a/CaseBi/Arr.hs
+++ b/CaseBi/Arr.hs
@@ -52,7 +52,7 @@
 you can reduce the needed amount of computations in the 'getBFst''.
 -}
 getBFst''
-  :: Ord a => (# Int, (a, b) #) -- ^ The first unboxed tuple of the index and the element of the array.
+  :: (Ord a, Ix i) => (# Int, (a, b) #) -- ^ The first unboxed tuple of the index and the element of the array.
   -> (# Int, (a, b) #) -- ^ The second unboxed tuple of the index and the element of the array.
   -> Array i (a, b) -- ^ The array of the pairs of the compared value and the result that is used in case the last argument is equal to the compared value.
   -> b -- ^ The default value that is used if no first element in the array tuples equals to the compared value.
@@ -64,7 +64,7 @@
 {-# INLINE getBFst'' #-}
 
 -- | The meaning of the arguments is the same as for 'getBFst'''. Is used internally in it. 
-gBF3 :: Ord a => (# Int#, (a, b) #) -> (# Int#, (a, b) #) -> Array i (a, b) -> b -> a -> b
+gBF3 :: (Ord a, Ix i) => (# Int#, (a, b) #) -> (# Int#, (a, b) #) -> Array i (a, b) -> b -> a -> b
 gBF3 (# !i#, k #) (# !j#, m #) arr def x
  | isTrue# ((j# -# i#) ># 1# ) = 
     case compare x (fst p) of
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:             0.1.2.0
+version:             0.1.3.0
 synopsis:            A library with less dependencies that can be used for multiple Ord a => a -> b transformations.
 description:         A library that can be used as a @case ... of@ constuction analogue for the multiple @Ord a => a -> b@ transformations and data representation. Uses "GHC.Arr" internally. If you use the module in GHCi, then, please, run the interpreter with the flag -fobject-code.
 homepage:            https://hackage.haskell.org/package/mmsyn2-array