Can't build a ghc cloned from github

There appears to be a bad ref on the server for the Cabal repo: == running git submodule update error: Unable to find b4d0c0f2846542dc2e2df189fe145a56ac9b30b6 under http://darcs.haskell.org/libraries/Cabal.git Cannot obtain needed object b4d0c0f2846542dc2e2df189fe145a56ac9b30b6 while processing commit e7e7ce1029707a67d26e6dc29de11141734898e3. error: Fetch failed. Unable to fetch in submodule path 'libraries/Cabal' git failed: 256 at ./sync-all line 116.