diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index f708603..71146a3 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -18,6 +18,8 @@ jobs:
 #           - windows-2019
           - windows-2022
         ghc:
+          - 8.4.4
+          - 8.6.5
           - 8.8.2
           - 8.10.7
           - 9.0.2
diff --git a/README.md b/README.md
index 38f36f2..61bf6ff 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ cabal update && cabal install darcs
 ```
 
 with a recent cabal (version 3.2 or later is recommended). Any version of
-ghc from 8.8 up to 9.8 should work.
+ghc from 8.2 up to 9.8 should work.
 
 From inside a clone or a source dist, use
 
diff --git a/darcs.cabal b/darcs.cabal
index b77dd4c..ee9558f 100644
--- a/darcs.cabal
+++ b/darcs.cabal
@@ -123,7 +123,7 @@ flag warn-as-error
 -- ----------------------------------------------------------------------
 
 custom-setup
-    setup-depends: base      >= 4.13 && < 4.20,
+    setup-depends: base      >= 4.10 && < 4.20,
                    Cabal     >= 2.4 && < 3.11,
                    process   >= 1.2.3.0 && < 1.7,
                    filepath  >= 1.4.1 && < 1.5.0.0,
@@ -412,7 +412,7 @@ Library
     else
       build-depends:  unix >= 2.7.1.0 && < 2.9
 
-    build-depends:    base              >= 4.13 && < 4.20,
+    build-depends:    base              >= 4.10 && < 4.20,
                       safe              >= 0.3.20 && < 0.4,
                       stm               >= 2.1 && < 2.6,
                       binary            >= 0.5 && < 0.11,
diff --git a/harness/Darcs/Test/Patch/Examples/Unwind.hs b/harness/Darcs/Test/Patch/Examples/Unwind.hs
index ae74b8c..cd5bfa7 100644
--- a/harness/Darcs/Test/Patch/Examples/Unwind.hs
+++ b/harness/Darcs/Test/Patch/Examples/Unwind.hs
@@ -8,6 +8,7 @@
 {-# LANGUAGE NoMonomorphismRestriction #-}
 {-# LANGUAGE PartialTypeSignatures #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE CPP #-}
 module Darcs.Test.Patch.Examples.Unwind where
 
 import Darcs.Prelude
@@ -37,6 +38,9 @@ import Darcs.Test.Patch.V1Model
 import Darcs.Test.Patch.WithState
 import Darcs.Test.TestOnly.Instance ()
 
+#if MIN_VERSION_base(4,12,0) && !MIN_VERSION_base(4,13,0)
+import Control.Monad.Fail
+#endif
 import Data.ByteString.Char8 ( pack )
 import qualified Data.ByteString.Lazy.Char8 as BLC
 import Data.Constraint
@@ -236,7 +240,9 @@ instance Applicative ErrorFail where
   liftA2 f (ErrorFail v1) (ErrorFail v2) = ErrorFail (f v1 v2)
 instance Monad ErrorFail where
   ErrorFail v >>= f = f v
+#if MIN_VERSION_base(4,12,0)
 instance MonadFail ErrorFail where
+#endif
   fail = error
 
 -- For now this code isn't used, it just demonstrates how example4 is broken in V1
diff --git a/shelly/src/Shelly.hs b/shelly/src/Shelly.hs
index b6e38ae..bfed3cc 100644
--- a/shelly/src/Shelly.hs
+++ b/shelly/src/Shelly.hs
@@ -124,6 +124,10 @@ import qualified Data.Text as T
 import qualified Data.ByteString as BS
 import Data.ByteString (ByteString)
 
+#if !MIN_VERSION_base(4,13,0)
+import Data.Monoid (mempty, mappend, (<>))
+#endif
+
 import Filesystem.Path.CurrentOS hiding (concat, fromText, (</>), (<.>))
 import Filesystem hiding (canonicalizePath)
 import qualified Filesystem.Path.CurrentOS as FP
diff --git a/shelly/src/Shelly/Base.hs b/shelly/src/Shelly/Base.hs
index fc0f488..4e45aac 100644
--- a/shelly/src/Shelly/Base.hs
+++ b/shelly/src/Shelly/Base.hs
@@ -40,12 +40,18 @@ import System.IO ( Handle, hFlush, stderr, stdout )
 import Control.Monad (when, (>=>))
 import Control.Monad.Base
 import Control.Monad.Trans.Control
+#if !MIN_VERSION_base(4,13,0)
+import Control.Applicative (Applicative, (<$>))
+#endif
 import Filesystem (isDirectory, listDirectory)
 import System.PosixCompat.Files( getSymbolicLinkStatus, isSymbolicLink )
 import Filesystem.Path.CurrentOS (FilePath, encodeString, relative)
 import qualified Filesystem.Path.CurrentOS as FP
 import qualified Filesystem as FS
 import Data.IORef (readIORef, modifyIORef, IORef)
+#if !MIN_VERSION_base(4,13,0)
+import Data.Monoid (mappend)
+#endif
 import qualified Data.Text as T
 import qualified Data.Text.IO as TIO
 import Control.Exception (SomeException, catch, throwIO, Exception)
@@ -65,8 +71,10 @@ newtype Sh a = Sh {
       unSh :: ReaderT (IORef State) IO a
   } deriving (Applicative, Monad, MonadIO, MonadReader (IORef State), Functor, Catch.MonadMask)
 
+#if MIN_VERSION_base(4,13,0)
 instance MonadFail Sh where
   fail = liftIO . fail
+#endif
 
 instance MonadBase IO Sh where
     liftBase = Sh . ReaderT . const
diff --git a/shelly/src/Shelly/Find.hs b/shelly/src/Shelly/Find.hs
index 846a25c..08b89d9 100644
--- a/shelly/src/Shelly/Find.hs
+++ b/shelly/src/Shelly/Find.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE OverloadedStrings #-}
 -- | File finding utiliites for Shelly
 -- The basic 'find' takes a dir and gives back a list of files.
@@ -11,6 +12,9 @@ module Shelly.Find
 import Prelude hiding (FilePath)
 import Shelly.Base
 import Control.Monad (foldM)
+#if !MIN_VERSION_base(4,13,0)
+import Data.Monoid (mappend)
+#endif
 import System.PosixCompat.Files( getSymbolicLinkStatus, isSymbolicLink )
 import Filesystem (isDirectory)
 import Filesystem.Path.CurrentOS (encodeString)
diff --git a/src/Darcs/Prelude.hs b/src/Darcs/Prelude.hs
index 5692864..1a82a89 100644
--- a/src/Darcs/Prelude.hs
+++ b/src/Darcs/Prelude.hs
@@ -27,6 +27,7 @@ module Darcs.Prelude
     ( module Prelude
     , module Control.Applicative
     , module Data.Monoid
+    , Semigroup(..)
     , module Data.Traversable
     ) where
 
@@ -41,6 +42,11 @@ import Prelude hiding
     ,
       -- because it's in the new Prelude but only in Data.Monoid in older GHCs
       Monoid(..)
+#if MIN_VERSION_base(4,11,0)
+    ,
+      -- because it's in the new Prelude but only in Data.Semigroup in older GHCs
+      Semigroup(..)
+#endif
     ,
       -- because it's in the new Prelude but only in Data.Traversable in older GHCs
       traverse
@@ -57,4 +63,5 @@ import Prelude hiding
 
 import Control.Applicative ( Applicative(..), (<$>), (<*>) )
 import Data.Monoid ( Monoid(..) )
+import Data.Semigroup ( Semigroup(..) )
 import Data.Traversable ( traverse )
diff --git a/src/Darcs/Util/Regex.hs b/src/Darcs/Util/Regex.hs
index 5a9be4f..8929ef1 100644
--- a/src/Darcs/Util/Regex.hs
+++ b/src/Darcs/Util/Regex.hs
@@ -1,4 +1,5 @@
 -- | This module is a subset of the defunct regex-compat-tdfa.
+{-# LANGUAGE CPP #-}
 module Darcs.Util.Regex
     ( Regex
     , mkRegex
@@ -9,6 +10,9 @@ module Darcs.Util.Regex
 import Darcs.Prelude
 
 import Control.Exception ( throw )
+#if !MIN_VERSION_base(4,13,0)
+import Control.Monad.Fail
+#endif
 import Text.Regex.Base
     ( RegexContext(matchM)
     , RegexMaker(makeRegexOptsM)
@@ -23,7 +27,16 @@ newtype RegexFail a = RegexFail { runRegexFail :: Either String a }
   -- The subtlety here is that only in base-4.13.0 the fail method
   -- in class Monad was removed. For earlier versions, regex-tdfa
   -- calls the fail from class Monad, not the one from class MonadFail.
+#if MIN_VERSION_base(4,13,0)
   deriving (Functor, Applicative, Monad)
+#else
+  deriving (Functor, Applicative)
+
+instance Monad RegexFail where
+  RegexFail (Left e) >>= _ = RegexFail (Left e)
+  RegexFail (Right r) >>= k = k r
+  fail = RegexFail . Left
+#endif
 
 instance MonadFail RegexFail where
   fail = RegexFail . Left
diff --git a/tests/issue2333.sh b/tests/issue2333.sh
index b157121..afa8acc 100644
--- a/tests/issue2333.sh
+++ b/tests/issue2333.sh
@@ -3,13 +3,6 @@
 
 . lib                           # Load some portability helpers.
 
-require_ghc 706
-
-# work around issue2720 (MacOS)
-if test -x /usr/bin/security; then
-  ln -s /usr/bin/security .
-fi
-
 darcs init      --repo R        # Create our test repos.
 darcs init      --repo S