diff --git a/codex.cabal b/codex.cabal
--- a/codex.cabal
+++ b/codex.cabal
@@ -1,5 +1,5 @@
 name:                codex
-version:             0.0.1.4
+version:             0.0.1.5
 synopsis:            A ctags file generator for cabal project dependencies.
 description:         
   This tool download and cache the source code of packages in your local hackage,
diff --git a/src/Codex.hs b/src/Codex.hs
--- a/src/Codex.hs
+++ b/src/Codex.hs
@@ -62,7 +62,7 @@
   fileExist <- tryIO $ doesFileExist file
   if fileExist then do
     content <- tryIO $ TLIO.readFile file
-    let hash = TextL.toStrict . TextL.drop 13 . head . drop 2 $ TextL.lines content
+    let hash = TextL.toStrict . TextL.drop 17 . head . drop 2 $ TextL.lines content
     return $ hash /= (Text.pack $ dependenciesHash is)
   else 
     return True
@@ -108,5 +108,5 @@
   tags i = packageTags cx i
   headers :: [TextL.Text]
   headers = fmap TextL.pack ["!_TAG_FILE_FORMAT 2", "!_TAG_FILE_SORTED 1", hash]
-  hash = concat ["!_CODEX_HASH ", dependenciesHash is]
+  hash = concat ["!_TAG_FILE_CODEX ", dependenciesHash is]
 
diff --git a/src/Main.hs b/src/Main.hs
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -83,6 +83,7 @@
           , "             [--help]"
           , ""
           , " update                Synchronize the `codex.tags` file in the current cabal project directory"
+          , " update --force        Discard `codex.tags` file hash and force regeneration"
           , " cache clean           Remove all `tags` file from the local hackage cache]"
           , " set tagger <tagger>   Update the `~/.codex` configuration file for the given tagger (hasktags|ctags)."
           , ""