diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+1.2.2
+-----
+* Added `foreign-var` support.
+
 1.2.1
 -----
 * Added `phantom` to `Data.Functor.Contravariant`. This combinator was formerly called `coerce` in the `lens` package, but
diff --git a/contravariant.cabal b/contravariant.cabal
--- a/contravariant.cabal
+++ b/contravariant.cabal
@@ -1,6 +1,6 @@
 name:          contravariant
 category:      Control, Data
-version:       1.2.1
+version:       1.2.2
 license:       BSD3
 cabal-version: >= 1.6
 license-file:  LICENSE
@@ -37,19 +37,30 @@
   default: True
   manual: True
 
+flag foreign-var
+  description:
+    You can disable the use of the `foreign-var` package on older versons of GHC using `-f-foreign-var`.
+    .
+    Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
+  default: True
+  manual: True
+
 library
   hs-source-dirs: src
   build-depends:
-    base < 5,
-    transformers >= 0.2 && < 0.5,
-    transformers-compat >= 0.3 && < 1,
-    void >= 0.6 && < 1
+    base                              < 5,
+    transformers        >= 0.2 &&     < 0.5,
+    transformers-compat >= 0.3 &&     < 1,
+    void                >= 0.6 &&     < 1
 
   if flag(tagged) && !impl(ghc >= 7.7)
     build-depends: tagged >= 0.4.4 && < 1
 
   if flag(semigroups)
     build-depends: semigroups >= 0.15.2 && < 1
+
+  if flag(foreign-var)
+    build-depends: foreign-var < 1
 
   if impl(ghc >= 7.4 && < 7.6)
     build-depends: ghc-prim
diff --git a/src/Data/Functor/Contravariant.hs b/src/Data/Functor/Contravariant.hs
--- a/src/Data/Functor/Contravariant.hs
+++ b/src/Data/Functor/Contravariant.hs
@@ -88,6 +88,10 @@
 
 import Data.Void
 
+#ifdef MIN_VERSION_foreign_var
+import Foreign.Var
+#endif
+
 #if __GLASGOW_HASKELL__ >= 702
 #define GHC_GENERICS
 import GHC.Generics
@@ -190,6 +194,12 @@
 instance Contravariant f => Contravariant (Reverse f) where
   contramap f = Reverse . contramap f . getReverse
   {-# INLINE contramap #-}
+
+#ifdef MIN_VERSION_foreign_var
+instance Contravariant SettableVar where
+  contramap f (SettableVar k) = SettableVar (k . f)
+  {-# INLINE contramap #-}
+#endif
 
 #if (__GLASGOW_HASKELL__ >= 707) || defined(VERSION_tagged)
 instance Contravariant Proxy where
diff --git a/src/Data/Functor/Contravariant/Divisible.hs b/src/Data/Functor/Contravariant/Divisible.hs
--- a/src/Data/Functor/Contravariant/Divisible.hs
+++ b/src/Data/Functor/Contravariant/Divisible.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 module Data.Functor.Contravariant.Divisible
   (
   -- * Contravariant Applicative
@@ -10,6 +11,10 @@
 import Data.Monoid
 import Data.Void
 
+#if MIN_VERSION_foreign_var
+import Foreign.Var
+#endif
+
 --------------------------------------------------------------------------------
 -- * Contravariant Applicative
 --------------------------------------------------------------------------------
@@ -77,7 +82,6 @@
 conquered :: Divisible f => f ()
 conquered = conquer
 
-
 -- |
 -- This is the divisible analogue of 'liftA'. It gives a viable default definition for 'contramap' in terms
 -- of the members of 'Divisible'.
@@ -110,6 +114,13 @@
     (b, c) -> g b && h c
   conquer = Predicate $ const True
 
+#if MIN_VERSION_foreign_var
+instance Divisible SettableVar where
+  divide k (SettableVar l) (SettableVar r) = SettableVar $ \ a -> case k a of
+    (b, c) -> l b >> r c
+  conquer = SettableVar $ \_ -> return ()
+#endif
+
 --------------------------------------------------------------------------------
 -- * Contravariant Alternative
 --------------------------------------------------------------------------------
@@ -177,3 +188,11 @@
 instance Monoid r => Decidable (Op r) where
   lose f = Op $ absurd . f
   choose f (Op g) (Op h) = Op $ either g h . f
+
+#if MIN_VERSION_foreign_var
+instance Decidable SettableVar where
+  lose k = SettableVar (absurd . k)
+  choose k (SettableVar l) (SettableVar r) = SettableVar $ \ a -> case k a of
+    Left b -> l b
+    Right c -> r c
+#endif