diff --git a/compactable.cabal b/compactable.cabal
--- a/compactable.cabal
+++ b/compactable.cabal
@@ -1,7 +1,7 @@
 name:                compactable
-version:             0.1.2.0
+version:             0.1.2.1
 synopsis:            A typeclass for structures which can be catMaybed, filtered, and partitioned.
-description:         This provides polymorphic implimentations for filter, compact (catMaybes), and separate. It allows for higher performance implimentations to be used in place of defaults for all data structures, and endeavors to centerally document those implimentations. Compactable aims to be as general and unconstrained as possible, providing instances for non-Functors like Set, as well as some Contravariants (though not published here). Compactable fully subsumes Data.Witherable, offers more laws, and is more general.
+description:         This provides polymorphic implementations for filter, compact (catMaybes), and separate. It allows for higher performance implementations to be used in place of defaults for all data structures, and endeavors to centerally document those implementations. Compactable aims to be as general and unconstrained as possible, providing instances for non-Functors like Set, as well as some Contravariants (though not published here). Compactable fully subsumes Data.Witherable, offers more laws, and is more general.
 license:             BSD3
 license-file:        LICENSE
 author:              Isaac Shapira
@@ -11,6 +11,7 @@
 build-type:          Simple
 extra-source-files:  ChangeLog.md
 cabal-version:       >=1.10
+tested-with:         GHC == 8.4.1, GHC == 8.2.2, GHC == 8.0.2
 
 source-repository head
   type: git
@@ -21,11 +22,11 @@
   -- other-modules:
   -- other-extensions:
   ghc-options: -Wall
-  build-depends:       base         >= 4.9    && < 4.10.2
+  build-depends:       base         >= 4.9    && < 4.12
                      , containers   >= 0.5.7  && < 0.6
                      , transformers >= 0.5.2  && < 0.6
                      , vector       >= 0.11   && < 0.13
-                     , bifunctors   >= 5.4.2  && < 5.5
+                     , bifunctors   >= 5.4.2  && < 5.6
 
   hs-source-dirs:      src
   default-language:    Haskell2010
diff --git a/src/Control/Compactable.hs b/src/Control/Compactable.hs
--- a/src/Control/Compactable.hs
+++ b/src/Control/Compactable.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                        #-}
 {-# LANGUAGE ConstrainedClassMethods    #-}
 {-# LANGUAGE DefaultSignatures          #-}
 {-# LANGUAGE FlexibleContexts           #-}
@@ -38,7 +39,6 @@
 import           Control.Applicative
 import           Control.Arrow
 import           Control.Monad                   (MonadPlus, join)
-import           Control.Monad.Trans.Error       (Error)
 import           Control.Monad.Trans.Except
 import           Control.Monad.Trans.Maybe
 import           Data.Bifoldable
@@ -414,10 +414,17 @@
 
 newtype AltSum f a = AltSum { unAltSum :: f a }
     deriving (Functor, Applicative, Alternative)
-
+#if __GLASGOW_HASKELL__ > 840
 instance Alternative f => Monoid (AltSum f a) where
     mempty = empty
     AltSum a `mappend` AltSum b = AltSum (a <|> b)
+#else
+instance Alternative f => Semigroup (AltSum f a) where
+    AltSum a <> AltSum b = AltSum (a <|> b)
+instance Alternative f => Monoid (AltSum f a) where
+    mappend = (Data.Semigroup.<>)
+    mempty = empty
+#endif
 
 
 {-|
@@ -494,7 +501,6 @@
     {-# INLINEABLE compactFold #-}
 
 instance CompactFold Maybe
-instance (Monoid m, Error m) => CompactFold (Either m)
 instance CompactFold IO
 instance CompactFold ReadP
 instance CompactFold ReadPrec