diff --git a/cabal-install/src/Distribution/Client/CmdRepl.hs b/cabal-install/src/Distribution/Client/CmdRepl.hs
index 39468a8e545..53d2ccdc9d5 100644
--- a/cabal-install/src/Distribution/Client/CmdRepl.hs
+++ b/cabal-install/src/Distribution/Client/CmdRepl.hs
@@ -147,6 +147,7 @@ import Distribution.Types.VersionRange
   ( anyVersion
   , orLaterVersion
   )
+import Distribution.Types.ParStrat
 import Distribution.Utils.Generic
   ( safeHead
   )
@@ -467,6 +468,10 @@ replAction flags@NixStyleFlags{extraFlags = r@ReplFlags{..}, ..} targetStrings g
                in -- GHC considers the last unit passed to be the active one
                   other_units ++ active_unit_files
 
+            render_j Serial = "1"
+            render_j (UseSem n) = show @Int n
+            render_j (NumJobs mn) = maybe "" (show @Int) mn
+
         -- run ghc --interactive with
         runProgramInvocation verbosity $
           programInvocation ghcProg' $
@@ -475,7 +480,7 @@ replAction flags@NixStyleFlags{extraFlags = r@ReplFlags{..}, ..} targetStrings g
               , "-package-env"
               , "-" -- to ignore ghc.environment.* files
               , "-j"
-              , show (buildSettingNumJobs (buildSettings ctx))
+              , render_j (buildSettingNumJobs (buildSettings ctx))
               ]
                 : [ ["-unit", "@" ++ dir </> unit]
                   | unit <- unit_files_ordered