diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -17,3 +17,8 @@
 
 * Second version. Some documentation improvements because of the similar code snippets found in the various
 previous publications by the other authors. Added new functions and rewrite the existing ones.
+
+## 0.2.1.0 -- 2020-12-05
+
+* Second version revised A. Fixed issue with being wrongly defined for the meanD and meanF functions.
+
diff --git a/Numeric/Stats.hs b/Numeric/Stats.hs
--- a/Numeric/Stats.hs
+++ b/Numeric/Stats.hs
@@ -22,8 +22,8 @@
 mean2F :: [Float] -> Float# -> Int# -> Float
 mean2F ((F# !x):xs) !s1 !l1 = mean2F xs (plusFloat# s1 x) (l1 +# 1#)
 mean2F _ !s1 !l1 =
- case l1 ==# 0# of
-  0# -> error "Not defined for the third zero argument. "
+ case I# l1 of
+  0 -> error "Not defined for the third zero argument. "
   _  -> F# m
    where !m = divideFloat# s1 (int2Float# l1)
 
@@ -35,8 +35,8 @@
 mean2D :: [Double] -> Double# -> Int# -> Double
 mean2D ((D# !x):xs) !s1 !l1 = mean2D xs (s1 +## x) (l1 +# 1#)
 mean2D _ !s1 !l1 =
- case l1 ==# 0# of
-  0# -> error "Not defined for the third zero argument. "
+ case I# l1 of
+  0 -> error "Not defined for the third zero argument. "
   _  -> D# m
    where !m = s1 /## int2Double# l1
 
diff --git a/uniqueness-periods-vector-stats.cabal b/uniqueness-periods-vector-stats.cabal
--- a/uniqueness-periods-vector-stats.cabal
+++ b/uniqueness-periods-vector-stats.cabal
@@ -2,7 +2,7 @@
 -- For further documentation, see http://haskell.org/cabal/users-guide/
 
 name:                uniqueness-periods-vector-stats
-version:             0.2.0.0
+version:             0.2.1.0
 synopsis:            A very basic descriptive statistics.
 description:         A very basic descriptive statistics. Functions use a tail recursion approach to compute the values and are strict by an accumulator.
 homepage:            https://hackage.haskell.org/package/uniqueness-periods-vector-stats