diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,10 @@
 # Revision history for butcher
 
+## 1.3.0.1  -- April 2018
+
+* Support ghc-8.4
+* Drop support for ghc<8
+
 ## 1.3.0.0  -- February 2018
 
 * Experimental: Hidden commandparts (do not appear in help)
diff --git a/butcher.cabal b/butcher.cabal
--- a/butcher.cabal
+++ b/butcher.cabal
@@ -1,12 +1,12 @@
 name:                butcher
-version:             1.3.0.0
+version:             1.3.0.1
 synopsis:            Chops a command or program invocation into digestable pieces.
 description:         See the <https://github.com/lspitzner/butcher/blob/master/README.md README> (it is properly formatted on github).
 license:             BSD3
 license-file:        LICENSE
 author:              Lennart Spitzner
 maintainer:          Lennart Spitzner <hexagoxel@hexagoxel.de>
-copyright:           Copyright (C) 2016-2017 Lennart Spitzner
+copyright:           Copyright (C) 2016-2018 Lennart Spitzner
 category:            UI
 build-type:          Simple
 Stability:           experimental
@@ -24,11 +24,6 @@
   location: https://github.com/lspitzner/butcher.git
 }
 
-flag butcher-dev
-  description: dev options
-  default: False
-  manual: True
-
 library
   exposed-modules:     UI.Butcher.Monadic.Types
                        UI.Butcher.Monadic
@@ -42,25 +37,21 @@
   other-modules:       UI.Butcher.Monadic.Internal.Types
                        UI.Butcher.Monadic.Internal.Core
   build-depends:
-    { base >=4.8 && <4.11
-    , free
-    , unsafe
+    { base >=4.9 && <4.12
+    , free < 5.1
+    , unsafe < 0.1
     , microlens <0.5
     , microlens-th <0.5
-    , multistate
-    , pretty
-    , containers
-    , transformers
-    , mtl
-    , extra
-    , void
-    , bifunctors
-    , deque
+    , multistate >=0.8 && <0.9
+    , pretty <1.2
+    , containers <0.6
+    , transformers <0.6
+    , mtl <2.3
+    , extra <1.7
+    , void <0.8
+    , bifunctors <5.6
+    , deque <0.3
     }
-  if flag(butcher-dev) {
-    build-depends:
-      hspec
-  }
   hs-source-dirs:      src
   default-language:    Haskell2010
   default-extensions: {
@@ -93,9 +84,6 @@
     -fno-warn-unused-imports
     -fno-warn-orphans
   }
-  if flag(butcher-dev) {
-    ghc-options: -O0 -Werror -fprof-auto -fprof-cafs
-  }
   include-dirs:
     srcinc
 
@@ -103,7 +91,7 @@
   type:             exitcode-stdio-1.0
   default-language: Haskell2010
   build-depends:
-    { base >=4.8 && <4.11
+    { base <999
     , butcher
     , free
     , unsafe
@@ -116,14 +104,8 @@
     , mtl
     , extra
     , deque
+    , hspec
     }
-  if flag(butcher-dev) {
-    buildable:        True
-    build-depends:
-      hspec
-  } else {
-    buildable:        False
-  }
   ghc-options:      -Wall
   main-is:          TestMain.hs
   other-modules:    
@@ -149,7 +131,3 @@
     -fno-warn-unused-imports
     -fno-warn-orphans
   }
-  if flag(butcher-dev) {
-    ghc-options: -Werror -fprof-auto -fprof-cafs -O0
-  }
-
diff --git a/src/UI/Butcher/Monadic/Flag.hs b/src/UI/Butcher/Monadic/Flag.hs
--- a/src/UI/Butcher/Monadic/Flag.hs
+++ b/src/UI/Butcher/Monadic/Flag.hs
@@ -80,14 +80,20 @@
   , _flag_visibility :: Visibility
   }
 
+appendFlag :: Flag p -> Flag p -> Flag p
+appendFlag (Flag a1 b1 c1) (Flag a2 b2 c2) = Flag (a1 <|> a2)
+                                                  (b1 <|> b2)
+                                                  (appVis c1 c2)
+ where
+  appVis Visible Visible = Visible
+  appVis _       _       = Hidden
+
+instance Semigroup (Flag p) where
+  (<>) = appendFlag
+
 instance Monoid (Flag p) where
   mempty = Flag Nothing Nothing Visible
-  Flag a1 b1 c1 `mappend` Flag a2 b2 c2 = Flag (a1 <|> a2)
-                                               (b1 <|> b2)
-                                               (appVis c1 c2)
-   where
-    appVis Visible Visible = Visible
-    appVis _       _       = Hidden
+  mappend = appendFlag
 
 -- | Create a 'Flag' with just a help text.
 flagHelp :: PP.Doc -> Flag p
diff --git a/src/UI/Butcher/Monadic/Param.hs b/src/UI/Butcher/Monadic/Param.hs
--- a/src/UI/Butcher/Monadic/Param.hs
+++ b/src/UI/Butcher/Monadic/Param.hs
@@ -55,17 +55,20 @@
   , _param_suggestions :: Maybe [CompletionItem]
   }
 
+appendParam :: Param p -> Param p -> Param p
+appendParam (Param a1 b1 c1) (Param a2 b2 c2) = Param (a1 `f` a2)
+                                                      (b1 `mappend` b2)
+                                                      (c1 `mappend` c2)
+ where
+  f Nothing x = x
+  f x       _ = x
+
+instance Semigroup (Param p) where
+  (<>) = appendParam
+
 instance Monoid (Param p) where
   mempty = Param Nothing Nothing Nothing
-  mappend (Param a1 b1 c1)
-          (Param a2 b2 c2)
-    = Param
-          (a1 `f` a2)
-          (b1 `mappend` b2)
-          (c1 `mappend` c2)
-    where
-      f Nothing x = x
-      f x       _ = x
+  mappend = appendParam
 
 -- | Create a 'Param' with just a help text.
 paramHelpStr :: String -> Param p
diff --git a/src/UI/Butcher/Monadic/Pretty.hs b/src/UI/Butcher/Monadic/Pretty.hs
--- a/src/UI/Butcher/Monadic/Pretty.hs
+++ b/src/UI/Butcher/Monadic/Pretty.hs
@@ -325,7 +325,7 @@
       sgsDocs ->
         PP.parens $ PP.fcat $ PP.punctuate (PP.text "|") $ sgsDocs ++ [d]
   PartRedirect s _ -> Just $ PP.text s
-  PartMany p       -> rec p <&> (<> PP.text "+")
+  PartMany p       -> rec p <&> (PP.<> PP.text "+")
   PartWithHelp _ p -> rec p
   PartReorder ps ->
     let flags  = [ d | PartMany d <- ps ]
diff --git a/srcinc/prelude.inc b/srcinc/prelude.inc
--- a/srcinc/prelude.inc
+++ b/srcinc/prelude.inc
@@ -123,6 +123,7 @@
 import System.IO ( IO )
 import Data.Proxy ( Proxy(..) )
 import Data.Sequence ( Seq )
+import Data.Semigroup ( Semigroup(..) )
 
 import Data.Map ( Map )
 import Data.Set ( Set )
@@ -336,8 +337,7 @@
 import Foreign.ForeignPtr                 ( ForeignPtr
                                           )
 
-import Data.Monoid                        ( (<>)
-                                          , mconcat
+import Data.Monoid                        ( mconcat
                                           , Monoid (..)
                                           )
 
@@ -388,6 +388,7 @@
 import Control.Monad.Trans.MultiRWS       ( MonadMultiReader(..)
                                           , MonadMultiWriter(..)
                                           , MonadMultiState(..)
+                                          , MonadMultiGet(..)
                                           )
 
 import Control.Monad.Trans.MultiReader    ( runMultiReaderTNil