And now it is much more complete. The 'hprotoc' compiler for proto files to Haskell source code now takes a "-u" command-line option. When given, this turns on code generation to support loading, storing, and saving unknown fields. The master source code archive has been broken up into the three corresponding Haskell packages: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/protocol-buffers http://hackage.haskell.org/cgi-bin/hackage-scripts/package/protocol-buffers-... http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hprotoc The latest version is 0.3.1. They must be installed in the order given above (and all have been tested with the "cabal-install" command). In addition the new unknown field support, a few small bugs were fixed. In the future I will look at the new extensible proto file option and see how such support could be added to this Haskell project. Cheers, Chris