To regenerate the plugin haskell files, please run hprotoc -u --prefix=Text -d protoc-gen-haskell -I google-proto-files/ google/protobuf/plugin.proto This was last populated from version 2.4.0a of Google's code. Also, one can invoke cabal build to make dist/autogen and then ghci -package parsec-2.1.0.1 -idist/build/autogen -iprotoc-gen-haskell Text/ProtocolBuffers/ProtoCompile.hs should work.