diff --git a/cabal-install/src/Distribution/Client/VCS.hs b/cabal-install/src/Distribution/Client/VCS.hs
index 41565586d95..ecca1637eb7 100644
--- a/cabal-install/src/Distribution/Client/VCS.hs
+++ b/cabal-install/src/Distribution/Client/VCS.hs
@@ -638,9 +638,9 @@ vcsGit =
           ["clone" ]
             ++ depthIs1
             ++ [ "--no-checkout", loc, localDir]
-            ++ case peer of
+            ++ (case peer of
               Nothing -> []
-              Just peerLocalDir -> ["--reference", peerLocalDir]
+              Just peerLocalDir -> ["--reference", peerLocalDir])
             ++ verboseArg
           where
             loc = srpLocation