diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,4 +1,9 @@
-# Changes in 1.1.0.0
+# Changes in 1.1.1
+
+- `Unbox` instance for `BinomAcc` is added.
+
+
+# Changes in 1.1.0
 
 - Type classes `CalcMean` and `CalcVar` are generalized to use `MonadThrow` to
   signal failure instead of using `Maybe` only
diff --git a/Data/Monoid/Statistics/Numeric.hs b/Data/Monoid/Statistics/Numeric.hs
--- a/Data/Monoid/Statistics/Numeric.hs
+++ b/Data/Monoid/Statistics/Numeric.hs
@@ -475,6 +475,12 @@
   [| \(Weighted w a) -> (w,a) |]
   [| \(w,a) -> Weighted w a   |]
 
+derivingUnbox "BinomAcc"
+  [t| BinomAcc -> (Int,Int)   |]
+  [| \(BinomAcc k n) -> (k,n) |]
+  [| \(k,n) -> BinomAcc k n   |]
+
+
 -- $references
 --
 -- * [Welford1962] Welford, B.P. (1962) Note on a method for
diff --git a/monoid-statistics.cabal b/monoid-statistics.cabal
--- a/monoid-statistics.cabal
+++ b/monoid-statistics.cabal
@@ -1,5 +1,5 @@
 Name:           monoid-statistics
-Version:        1.1.0
+Version:        1.1.1
 Cabal-Version:  >= 1.10
 License:        BSD3
 License-File:   LICENSE