diff --git a/src/compiler/GF/Command/Commands.hs b/src/compiler/GF/Command/Commands.hs
index 3ca2ab962..a8a175f7c 100644
--- a/src/compiler/GF/Command/Commands.hs
+++ b/src/compiler/GF/Command/Commands.hs
@@ -3,7 +3,7 @@ module GF.Command.Commands (
   PGFEnv,HasPGFEnv(..),pgf,mos,pgfEnv,pgfCommands,
   options,flags,
   ) where
-import Prelude hiding (putStrLn)
+import Prelude hiding (putStrLn,(<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import PGF
 
diff --git a/src/compiler/GF/Command/Commands2.hs b/src/compiler/GF/Command/Commands2.hs
index 0cc5d7d23..b5335479c 100644
--- a/src/compiler/GF/Command/Commands2.hs
+++ b/src/compiler/GF/Command/Commands2.hs
@@ -3,7 +3,7 @@ module GF.Command.Commands2 (
   PGFEnv,HasPGFEnv(..),pgf,concs,pgfEnv,emptyPGFEnv,pgfCommands,
   options, flags,
   ) where
-import Prelude hiding (putStrLn)
+import Prelude hiding (putStrLn,(<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import PGF2
 import qualified PGF as H
diff --git a/src/compiler/GF/Compile/CheckGrammar.hs b/src/compiler/GF/Compile/CheckGrammar.hs
index 5c1743b74..1348d8e41 100644
--- a/src/compiler/GF/Compile/CheckGrammar.hs
+++ b/src/compiler/GF/Compile/CheckGrammar.hs
@@ -21,6 +21,7 @@
 -----------------------------------------------------------------------------
 
 module GF.Compile.CheckGrammar(checkModule) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import GF.Infra.Ident
 import GF.Infra.Option
diff --git a/src/compiler/GF/Compile/Compute/ConcreteNew.hs b/src/compiler/GF/Compile/Compute/ConcreteNew.hs
index a77da88bf..f9edc931c 100644
--- a/src/compiler/GF/Compile/Compute/ConcreteNew.hs
+++ b/src/compiler/GF/Compile/Compute/ConcreteNew.hs
@@ -5,6 +5,7 @@ module GF.Compile.Compute.ConcreteNew
             normalForm,
             Value(..), Bind(..), Env, value2term, eval, vapply
            ) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import GF.Grammar hiding (Env, VGen, VApp, VRecType)
 import GF.Grammar.Lookup(lookupResDefLoc,allParamValues)
diff --git a/src/compiler/GF/Compile/TypeCheck/RConcrete.hs b/src/compiler/GF/Compile/TypeCheck/RConcrete.hs
index 2fe08b256..88e324ff3 100644
--- a/src/compiler/GF/Compile/TypeCheck/RConcrete.hs
+++ b/src/compiler/GF/Compile/TypeCheck/RConcrete.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE PatternGuards #-}
 module GF.Compile.TypeCheck.RConcrete( checkLType, inferLType, computeLType, ppType ) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import GF.Infra.CheckM
 import GF.Data.Operations
diff --git a/src/compiler/GF/CompileInParallel.hs b/src/compiler/GF/CompileInParallel.hs
index 7986656ec..8420b1771 100644
--- a/src/compiler/GF/CompileInParallel.hs
+++ b/src/compiler/GF/CompileInParallel.hs
@@ -1,6 +1,6 @@
 -- | Parallel grammar compilation
 module GF.CompileInParallel(parallelBatchCompile) where
-import Prelude hiding (catch)
+import Prelude hiding (catch,(<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 import Control.Monad(join,ap,when,unless)
 import Control.Applicative
 import GF.Infra.Concurrency
diff --git a/src/compiler/GF/Grammar/Printer.hs b/src/compiler/GF/Grammar/Printer.hs
index dcd419c42..4b19d215b 100644
--- a/src/compiler/GF/Grammar/Printer.hs
+++ b/src/compiler/GF/Grammar/Printer.hs
@@ -22,6 +22,7 @@ module GF.Grammar.Printer
            , ppMeta
            , getAbs
            ) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import GF.Infra.Ident
 import GF.Infra.Option
diff --git a/src/compiler/GF/Haskell.hs b/src/compiler/GF/Haskell.hs
index e2156ac5d..57601c1d5 100644
--- a/src/compiler/GF/Haskell.hs
+++ b/src/compiler/GF/Haskell.hs
@@ -1,6 +1,7 @@
 -- | Abstract syntax and a pretty printer for a subset of Haskell
 {-# LANGUAGE DeriveFunctor #-}
 module GF.Haskell where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 import GF.Infra.Ident(Ident,identS)
 import GF.Text.Pretty
 
diff --git a/src/compiler/GF/Infra/CheckM.hs b/src/compiler/GF/Infra/CheckM.hs
index 3b6833f0f..c5f9ba255 100644
--- a/src/compiler/GF/Infra/CheckM.hs
+++ b/src/compiler/GF/Infra/CheckM.hs
@@ -18,6 +18,7 @@ module GF.Infra.CheckM
 	   checkIn, checkInModule, checkMap, checkMapRecover,
            parallelCheck, accumulateError, commitCheck,
 	  ) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import GF.Data.Operations
 --import GF.Infra.Ident
diff --git a/src/compiler/GF/Infra/Location.hs b/src/compiler/GF/Infra/Location.hs
index 0bf85b37f..8447a297c 100644
--- a/src/compiler/GF/Infra/Location.hs
+++ b/src/compiler/GF/Infra/Location.hs
@@ -1,5 +1,6 @@
 -- | Source locations
 module GF.Infra.Location where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 import GF.Text.Pretty
 
 -- ** Source locations
diff --git a/src/compiler/GF/Speech/GSL.hs b/src/compiler/GF/Speech/GSL.hs
index d9d6af0cc..a898a4bb5 100644
--- a/src/compiler/GF/Speech/GSL.hs
+++ b/src/compiler/GF/Speech/GSL.hs
@@ -7,6 +7,7 @@
 -----------------------------------------------------------------------------
 
 module GF.Speech.GSL (gslPrinter) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 --import GF.Data.Utilities
 import GF.Grammar.CFG
diff --git a/src/compiler/GF/Speech/JSGF.hs b/src/compiler/GF/Speech/JSGF.hs
index 25168dbc8..15f5ff69d 100644
--- a/src/compiler/GF/Speech/JSGF.hs
+++ b/src/compiler/GF/Speech/JSGF.hs
@@ -11,6 +11,7 @@
 -----------------------------------------------------------------------------
 
 module GF.Speech.JSGF (jsgfPrinter) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 --import GF.Data.Utilities
 import GF.Infra.Option
diff --git a/src/compiler/GF/Speech/SRGS_ABNF.hs b/src/compiler/GF/Speech/SRGS_ABNF.hs
index 75d206a0c..dc5c7bbd3 100644
--- a/src/compiler/GF/Speech/SRGS_ABNF.hs
+++ b/src/compiler/GF/Speech/SRGS_ABNF.hs
@@ -18,6 +18,7 @@
 -----------------------------------------------------------------------------
 
 module GF.Speech.SRGS_ABNF (srgsAbnfPrinter, srgsAbnfNonRecursivePrinter) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 --import GF.Data.Utilities
 import GF.Infra.Option
diff --git a/src/runtime/haskell-bind/PGF2.hsc b/src/runtime/haskell-bind/PGF2.hsc
index fb3672c0f..895d13ca4 100644
--- a/src/runtime/haskell-bind/PGF2.hsc
+++ b/src/runtime/haskell-bind/PGF2.hsc
@@ -82,7 +82,7 @@ module PGF2 (-- * PGF
              LiteralCallback,literalCallbacks
             ) where
 
-import Prelude hiding (fromEnum)
+import Prelude hiding (fromEnum,(<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 import Control.Exception(Exception,throwIO)
 import Control.Monad(forM_)
 import System.IO.Unsafe(unsafePerformIO,unsafeInterleaveIO)
diff --git a/src/runtime/haskell/Data/Binary/Builder.hs b/src/runtime/haskell/Data/Binary/Builder.hs
index 03531daa7..b69371f0e 100644
--- a/src/runtime/haskell/Data/Binary/Builder.hs
+++ b/src/runtime/haskell/Data/Binary/Builder.hs
@@ -100,6 +100,11 @@ newtype Builder = Builder {
         runBuilder :: (Buffer -> [S.ByteString]) -> Buffer -> [S.ByteString]
     }
 
+#if MIN_VERSION_base(4,11,0)
+instance Semigroup Builder where
+  (<>) = append
+#endif
+
 instance Monoid Builder where
     mempty  = empty
     {-# INLINE mempty #-}
diff --git a/src/runtime/haskell/PGF/ByteCode.hs b/src/runtime/haskell/PGF/ByteCode.hs
index 579d6b3bb..ef21ab229 100644
--- a/src/runtime/haskell/PGF/ByteCode.hs
+++ b/src/runtime/haskell/PGF/ByteCode.hs
@@ -2,7 +2,7 @@ module PGF.ByteCode(Literal(..),
                     CodeLabel, Instr(..), IVal(..), TailInfo(..),
                     ppLit, ppCode, ppInstr
                    ) where
-
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 import PGF.CId
 import Text.PrettyPrint
 
diff --git a/src/runtime/haskell/PGF/Macros.hs b/src/runtime/haskell/PGF/Macros.hs
index de175616c..3fc7a5804 100644
--- a/src/runtime/haskell/PGF/Macros.hs
+++ b/src/runtime/haskell/PGF/Macros.hs
@@ -1,4 +1,5 @@
 module PGF.Macros where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import PGF.CId
 import PGF.Data
diff --git a/src/runtime/haskell/PGF/Printer.hs b/src/runtime/haskell/PGF/Printer.hs
index 43c270b13..07e94f866 100644
--- a/src/runtime/haskell/PGF/Printer.hs
+++ b/src/runtime/haskell/PGF/Printer.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 module PGF.Printer (ppPGF,ppCat,ppFId,ppFunId,ppSeqId,ppSeq,ppFun) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import PGF.CId
 import PGF.Data
diff --git a/src/runtime/haskell/PGF/VisualizeTree.hs b/src/runtime/haskell/PGF/VisualizeTree.hs
index 5d884fafe..520eb59c3 100644
--- a/src/runtime/haskell/PGF/VisualizeTree.hs
+++ b/src/runtime/haskell/PGF/VisualizeTree.hs
@@ -23,6 +23,7 @@ module PGF.VisualizeTree
              , gizaAlignment
              , conlls2latexDoc
              ) where
+import Prelude hiding ((<>)) -- GHC 8.4.1 clash with Text.PrettyPrint
 
 import PGF.CId (wildCId,showCId,ppCId,mkCId) --CId,pCId,
 import PGF.Data