diff --git a/Backend/SHA1.hs b/Backend/SHA1.hs
index caece6b78c..9e8d6df6dd 100644
--- a/Backend/SHA1.hs
+++ b/Backend/SHA1.hs
@@ -3,6 +3,11 @@
 
 module Backend.SHA1 (backend) where
 
+import Control.Monad.State
+import Data.String.Utils
+import System.Cmd.Utils
+import System.IO
+
 import qualified Backend.File
 import TypeInternals
 
@@ -13,4 +18,9 @@ backend = Backend.File.backend {
 
 -- checksum the file to get its key
 keyValue :: FilePath -> Annex (Maybe Key)
-keyValue k = error "SHA1 keyValue unimplemented" -- TODO
+keyValue file = liftIO $ pOpen ReadFromPipe "sha1sum" [file] $ \h -> do
+		line <- hGetLine h
+		let bits = split " " line
+		if (null bits)
+			then error "sha1sum parse error"
+			else return $ Just $ Key ((name backend), bits !! 0)
diff --git a/GitRepo.hs b/GitRepo.hs
index ee1bdba344..9418102355 100644
--- a/GitRepo.hs
+++ b/GitRepo.hs
@@ -195,8 +195,8 @@ run repo params = assertLocal repo $ do
 pipeRead :: Repo -> [String] -> IO String
 pipeRead repo params = assertLocal repo $ do
 	pOpen ReadFromPipe "git" (gitCommandLine repo params) $ \h -> do
-	ret <- hGetContentsStrict h
-	return ret
+		ret <- hGetContentsStrict h
+		return ret
 
 {- Passed a location, recursively scans for all files that
  - are checked into git at that location. -}
diff --git a/doc/todo/backendSHA1.mdwn b/doc/todo/backendSHA1.mdwn
index 40ff868c22..fa9728af64 100644
--- a/doc/todo/backendSHA1.mdwn
+++ b/doc/todo/backendSHA1.mdwn
@@ -1 +1,5 @@
 This backend is not finished.
+
+In particular, while files can be added using it, git-annex will not notice
+when their content changes, and will not create a new key for the new sha1
+of the net content.