diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,3 +1,8 @@
+# Changes in 1.1.5
+
+- Bifunctor instance is added to `Weighted`
+
+
 # Changes in 1.1.4
 
 - Actually export `CountW`
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
@@ -59,6 +59,7 @@
   ) where
 
 import Control.Monad.Catch          (MonadThrow(..))
+import Data.Bifunctor
 import Data.Data                    (Typeable,Data)
 import Data.Vector.Unboxed          (Unbox)
 import Data.Vector.Unboxed.Deriving (derivingUnbox)
@@ -477,6 +478,13 @@
 data Weighted w a = Weighted w a
   deriving stock (Show,Eq,Ord,Data,Generic,Functor,Foldable,Traversable)
 
+instance Bifunctor Weighted where
+  first  f   (Weighted w a) = Weighted (f w) a
+  second f   (Weighted w a) = Weighted w (f a)
+  bimap  f g (Weighted w a) =Weighted (f w) (g a)
+  {-# INLINE first  #-}
+  {-# INLINE second #-}
+  {-# INLINE bimap  #-}
 
 
 ----------------------------------------------------------------
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:        1.1.4
+Version:        1.1.5
 Cabal-Version:  >= 1.10
 License:        BSD3
 License-File:   LICENSE
@@ -83,7 +83,7 @@
   default-language: Haskell2010
   build-depends:
         base                >=4.9  && <5
-      , doctest             >=0.15 && <0.21
+      , doctest             >=0.15 && <0.23
       , monoid-statistics   -any
 
 benchmark monoid-stat-bench