diff --git a/pred-trie.cabal b/pred-trie.cabal
--- a/pred-trie.cabal
+++ b/pred-trie.cabal
@@ -1,5 +1,5 @@
 Name:                   pred-trie
-Version:                0.0.10
+Version:                0.0.10.1
 Author:                 Athan Clark <athan.clark@gmail.com>
 Maintainer:             Athan Clark <athan.clark@gmail.com>
 License:                BSD3
@@ -21,9 +21,8 @@
                         Data.Trie.Pred.Hetero.Unified.Tail
                        -- Data.Trie.Pred.Hetero.Disjoint
                        -- Data.Trie.Pred.Hetero.Disjoint.Tail
-  Build-Depends:        base >= 4 && < 5
+  Build-Depends:        base >= 4.8 && < 5
                       , semigroups
-                      , bifunctors
 
 Test-Suite spec
   Type:                 exitcode-stdio-1.0
diff --git a/src/Data/Trie/Pred/Disjoint/Tail.hs b/src/Data/Trie/Pred/Disjoint/Tail.hs
--- a/src/Data/Trie/Pred/Disjoint/Tail.hs
+++ b/src/Data/Trie/Pred/Disjoint/Tail.hs
@@ -15,6 +15,7 @@
 
 import Prelude hiding (lookup)
 import Data.List.NonEmpty as NE hiding (map, sort)
+import Control.Applicative
 
 
 
diff --git a/src/Data/Trie/Pred/Hetero/Unified.hs b/src/Data/Trie/Pred/Hetero/Unified.hs
--- a/src/Data/Trie/Pred/Hetero/Unified.hs
+++ b/src/Data/Trie/Pred/Hetero/Unified.hs
@@ -13,6 +13,7 @@
 import qualified Data.Trie.Pred.Hetero.Unified.Tail as NU
 import Data.Monoid
 import qualified Data.List.NonEmpty as NE
+import Control.Applicative
 
 
 data RHUPTrie t a b = Rooted { root :: Maybe a
diff --git a/src/Data/Trie/Pred/Hetero/Unified/Tail.hs b/src/Data/Trie/Pred/Hetero/Unified/Tail.hs
--- a/src/Data/Trie/Pred/Hetero/Unified/Tail.hs
+++ b/src/Data/Trie/Pred/Hetero/Unified/Tail.hs
@@ -15,7 +15,7 @@
 
 import Prelude hiding (lookup)
 import Data.List.NonEmpty as NE hiding (map, sort)
--- import Data.Bifunctor (bimap)
+import Control.Applicative
 
 
 data HUPTrie t a b where
diff --git a/src/Data/Trie/Pred/Unified/Tail.hs b/src/Data/Trie/Pred/Unified/Tail.hs
--- a/src/Data/Trie/Pred/Unified/Tail.hs
+++ b/src/Data/Trie/Pred/Unified/Tail.hs
@@ -15,6 +15,7 @@
 
 import Prelude hiding (lookup)
 import Data.List.NonEmpty as NE hiding (map, sort)
+import Control.Applicative