diff --git a/src/Stack2nix/External/Util.hs b/src/Stack2nix/External/Util.hs
index c3543f3..c58a662 100644
--- a/src/Stack2nix/External/Util.hs
+++ b/src/Stack2nix/External/Util.hs
@@ -16,9 +16,13 @@ runCmdFrom dir prog args =
 runCmd :: String -> [String] -> IO (ExitCode, String, String)
 runCmd prog args = getCurrentDirectory >>= (\d -> runCmdFrom d prog args)
 
-failHard :: (ExitCode, String, String) -> IO (ExitCode, String, String)
-failHard r@(ExitSuccess, _, _)         = pure r
-failHard (ExitFailure code, _, stderr) =
+failHardWith :: String -> (ExitCode, String, String) -> IO (ExitCode, String, String)
+failHardWith _msg r@(ExitSuccess, _, _)        = pure r
+failHardWith msg (ExitFailure code, _, stderr) =
   error $ unlines [ "Failed with exit code " <> show code <> "..."
-                  , show stderr
+                  , stderr
+                  , msg
                   ]
+
+failHard :: (ExitCode, String, String) -> IO (ExitCode, String, String)
+failHard = failHardWith ""
diff --git a/src/Stack2nix/External/VCS/Git.hs b/src/Stack2nix/External/VCS/Git.hs
index 639bd79..b8ed678 100644
--- a/src/Stack2nix/External/VCS/Git.hs
+++ b/src/Stack2nix/External/VCS/Git.hs
@@ -3,7 +3,7 @@ module Stack2nix.External.VCS.Git
   , git
   ) where
 
-import           Stack2nix.External.Util (failHard, runCmd, runCmdFrom)
+import           Stack2nix.External.Util (failHardWith, runCmd, runCmdFrom)
 import           System.Exit             (ExitCode (..))
 
 data Command = OutsideRepo ExternalCmd
@@ -23,8 +23,8 @@ git (InsideRepo dir cmd) = runInternal dir cmd
 
 runExternal :: ExternalCmd -> IO (ExitCode, String, String)
 runExternal (Clone uri dir) =
-  runCmd exe ["clone", uri, dir] >>= failHard
+  runCmd exe ["clone", uri, dir] >>= failHardWith ("git: expected " ++ uri ++ " to be a repository, but it can't be cloned")
 
 runInternal :: FilePath -> InternalCmd -> IO (ExitCode, String, String)
 runInternal repoDir (Checkout ref) =
-  runCmdFrom repoDir exe ["checkout", ref] >>= failHard
+  runCmdFrom repoDir exe ["checkout", ref] >>= failHardWith ("git: failed to checkout revision " ++ ref)