diff --git a/codex.cabal b/codex.cabal
--- a/codex.cabal
+++ b/codex.cabal
@@ -1,5 +1,5 @@
 name:                codex
-version:             0.1.0.4
+version:             0.1.0.5
 synopsis:            A ctags file generator for cabal project dependencies.
 description:         
   This tool download and cache the source code of packages in your local hackage,
@@ -55,6 +55,7 @@
   build-depends:       
       base
     , Cabal
+    , bytestring
     , directory
     , either
     , filepath
@@ -63,4 +64,4 @@
     , monad-loops         >= 0.4.2      && < 0.5
     , transformers
     , yaml                >= 0.8.8.3    && < 0.9
-    , codex               == 0.1.0.4
+    , codex               == 0.1.0.5
diff --git a/codex/Main.hs b/codex/Main.hs
--- a/codex/Main.hs
+++ b/codex/Main.hs
@@ -31,8 +31,12 @@
 tagsFile :: FilePath
 tagsFile = joinPath ["codex.tags"]
 
+hashFile :: Codex -> FilePath
+hashFile cx = hackagePath cx </> "codex.hash"
+
 cleanCache :: Codex -> IO ()
 cleanCache cx = do
+  -- TODO Delete hash file!
   xs <- listDirectory hp
   ys <- fmap (rights) $ traverse (safe . listDirectory) xs
   zs <- traverse (safe . removeFile) . fmap (</> "tags") $ concat ys
@@ -43,6 +47,16 @@
       xs <- getDirectoryContents fp
       return . fmap (fp </>) $ filter (not . startswith ".") xs
 
+readCacheHash :: Codex -> IO (Maybe String)
+readCacheHash cx = do
+  fileExist <- doesFileExist $ hashFile cx
+  if not fileExist then return Nothing else do
+    content <- readFile $ hashFile cx
+    return $ Just content
+
+writeCacheHash :: Codex -> String -> IO ()
+writeCacheHash cx = writeFile $ hashFile cx
+
 update :: Codex -> Bool -> IO ()
 update cx force = do
   (project, dependencies, workspaceProjects) <- resolveCurrentProjectDependencies
@@ -104,7 +118,18 @@
 
     withConfig cx f = checkConfig cx >>= \state -> case state of
       TaggerNotFound  -> fail $ "codex: tagger not found."
-      Ready           -> f cx
+      Ready           -> do
+        cacheHash' <- readCacheHash cx
+        case cacheHash' of
+          Just cacheHash ->
+            when (cacheHash /= configHash) $ do
+              putStrLn "codex: configuration has been updated, cleaning cache ..."
+              cleanCache cx
+          Nothing -> return ()
+        res <- f cx
+        writeCacheHash cx configHash
+        return res where
+          configHash = hashConfig cx
 
     fail msg = do
       putStrLn $ msg
diff --git a/codex/Main/Config.hs b/codex/Main/Config.hs
--- a/codex/Main/Config.hs
+++ b/codex/Main/Config.hs
@@ -2,12 +2,15 @@
 {-# LANGUAGE StandaloneDeriving #-}
 module Main.Config where
 
+import Data.Hash.MD5
 import Data.Yaml
 import GHC.Generics
 
 import System.Directory
 import System.FilePath
 
+import qualified Data.ByteString.Char8 as BS
+
 import Codex
 
 import qualified Main.Config.Codex0 as C0
@@ -32,6 +35,9 @@
     _         -> TaggerNotFound
   where
     tagger = head $ words (tagsCmd cx)
+
+hashConfig :: Codex -> String
+hashConfig cfg = md5s . Str . BS.unpack $ encode cfg
 
 loadConfig :: IO Codex
 loadConfig = decodeConfig >>= maybe defaultConfig return where
diff --git a/src/Codex.hs b/src/Codex.hs
--- a/src/Codex.hs
+++ b/src/Codex.hs
@@ -123,7 +123,7 @@
       TLIO.writeFile o $ TextL.unlines (concat [headers, ys])
     tags i = packageTags cx i
     headers = if tagsFileHeader cx then fmap TextL.pack [headerFormat, headerSorted, headerHash] else []
-    headerFormat = "!_TAG_FILE_FORMAT 2"
-    headerSorted = concat ["!_TAG_FILE_SORTED ", if sorted then "1" else "0"]
-    headerHash = concat ["!_TAG_FILE_CODEX ", dependenciesHash dependencies]
+    headerFormat = "!_TAG_FILE_FORMAT\t2"
+    headerSorted = concat ["!_TAG_FILE_SORTED\t", if sorted then "1" else "0"]
+    headerHash = concat ["!_TAG_FILE_CODEX\t", dependenciesHash dependencies]
     sorted = tagsFileSorted cx
diff --git a/src/Codex/Project.hs b/src/Codex/Project.hs
--- a/src/Codex/Project.hs
+++ b/src/Codex/Project.hs
@@ -35,10 +35,11 @@
 identifier = package . packageDescription
 
 allDependencies :: GenericPackageDescription -> [Dependency]
-allDependencies pd = List.filter (not . isCurrent) $ concat [lds, eds, tds] where
+allDependencies pd = List.filter (not . isCurrent) $ concat [lds, eds, tds, bds] where
   lds = condTreeConstraints =<< (maybeToList $ condLibrary pd)
   eds = (condTreeConstraints . snd) =<< condExecutables pd
   tds = (condTreeConstraints . snd) =<< condTestSuites pd
+  bds = (condTreeConstraints . snd) =<< condBenchmarks pd
   isCurrent (Dependency n _) = n == (pkgName $ identifier pd)
 
 findPackageDescription :: FilePath -> IO (Maybe GenericPackageDescription)