diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,13 @@
 # Revision history for validationt
 
-## 0.1.0.0  -- YYYY-mm-dd
+## 0.2.1.0
 
-* First version. Released on an unsuspecting world.
+* GHC 8.4 support
+
+## 0.2.0.0
+
+* Fixes
+
+## 0.1.0.0
+
+* Initial release
diff --git a/src/Control/Monad/Validation.hs b/src/Control/Monad/Validation.hs
--- a/src/Control/Monad/Validation.hs
+++ b/src/Control/Monad/Validation.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE TemplateHaskell #-}
@@ -47,10 +48,14 @@
 instance (Ord k) => At (MonoidMap k v) where
   at key = _MonoidMap . at key
 
+#if MIN_VERSION_base(4,11,0)
+instance (Ord k, Semigroup v) => Semigroup (MonoidMap k v) where
+  (<>) = mmAppend
+#endif
+
 instance (Ord k, Monoid v) => Monoid (MonoidMap k v) where
   mempty = MonoidMap M.empty
-  mappend (MonoidMap a) (MonoidMap b) =
-    MonoidMap $ M.unionWith (<>) a b
+  mappend = mmAppend
 
 instance (ToJSON k, ToJSON v) => ToJSON (MonoidMap k v) where
   toJSON (MonoidMap m) = toJSON $ L.map toObj $ M.toList m
@@ -69,6 +74,13 @@
         key <- obj .: "id"
         val <- obj .: "value"
         return (key, val)
+
+#if MIN_VERSION_base(4,11,0)
+mmAppend :: (Ord k, Semigroup v) => MonoidMap k v -> MonoidMap k v -> MonoidMap k v
+#else
+mmAppend :: (Ord k, Monoid v) => MonoidMap k v -> MonoidMap k v -> MonoidMap k v
+#endif
+mmAppend (MonoidMap a) (MonoidMap b) = MonoidMap $ M.unionWith (<>) a b
 
 -- | Convenient for 'vZoom' as first artument. Will prevent generation
 -- of map with 'mempty' values
diff --git a/validationt.cabal b/validationt.cabal
--- a/validationt.cabal
+++ b/validationt.cabal
@@ -2,10 +2,10 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                validationt
-version:             0.2.0.0
-synopsis:            Straightforward validation monad. Convenient solution for validating web forms and APIs.
--- description:
-homepage:            typeable.io
+version:             0.2.1.0
+synopsis:            Straightforward validation monad.
+description:         Convenient solution for validating web forms and APIs.
+homepage:            https://github.com/typeable/validationt
 license:             BSD3
 license-file:        LICENSE
 author:              Typeable.io contributors
@@ -15,11 +15,17 @@
 build-type:          Simple
 extra-source-files:  ChangeLog.md
 cabal-version:       >=1.10
+tested-with:         GHC == 7.10.3
+                   , GHC == 8.0.2
+                   , GHC == 8.2.2
+                   , GHC == 8.4.1
 
+source-repository head
+  type:     git
+  location: git@github.com:typeable/validationt.git
+
 library
   exposed-modules:    Control.Monad.Validation
-  -- other-modules:
-  -- other-extensions:
   build-depends:       base >=4.8 && < 5
                      , aeson >= 1.0
                      , containers