diff --git a/cabal-install/Main.hs b/cabal-install/Main.hs
index 0ce0c2077e5..59bd968d8ee 100644
--- a/cabal-install/Main.hs
+++ b/cabal-install/Main.hs
@@ -140,7 +140,7 @@ import qualified Paths_cabal_install (version)
 
 import System.Environment       (getArgs, getProgName)
 import System.Exit              (exitFailure)
-import System.FilePath          (splitExtension, takeExtension)
+import System.FilePath          (splitExtension, takeExtension, searchPathSeparator)
 import System.IO                (BufferMode(LineBuffering),
                                  hSetBuffering, stdout)
 import System.Directory         (doesFileExist, getCurrentDirectory)
@@ -1046,7 +1046,8 @@ execAction execFlags extraArgs globalFlags = do
                 exitFailure
             Just ghcProg ->  do
                 g <- ghcGlobalPackageDB verbosity ghcProg
-                getEffectiveEnvironment [("GHC_PACKAGE_PATH", Just $ s ++ ":" ++ g)]
+                getEffectiveEnvironment
+                  [("GHC_PACKAGE_PATH", Just $ s ++ [searchPathSeparator] ++ g)]
 
 -- | See 'Distribution.Client.Install.withWin32SelfUpgrade' for details.
 --