diff --git a/cabal-install/Main.hs b/cabal-install/Main.hs
index bedfea4944893d56918a698f07ccb0ed45967ebe..5289e82820f6be6fb805f4ca15cf88946dc4ee43 100644
--- a/cabal-install/Main.hs
+++ b/cabal-install/Main.hs
@@ -1105,8 +1105,8 @@ sandboxAction sandboxFlags extraArgs globalFlags = do
         sandboxAddSource verbosity extra sandboxFlags globalFlags
     ("delete-source":extra) -> do
         when (noExtraArgs extra) $
-          die "The 'sandbox delete-source' command expects \
-              \at least one argument"
+          die ("The 'sandbox delete-source' command expects " ++
+              "at least one argument")
         sandboxDeleteSource verbosity extra sandboxFlags globalFlags
     ["list-sources"] -> sandboxListSources verbosity sandboxFlags globalFlags