google-cloud-ruby: DataStore protocol error?

Got this exception (Ruby) when reading from DataStore, as far as I understand it is while deserializing server response:

TypeError: wrong argument type false (expected String)
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/rpc_desc.rb:62:in `decode'
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/rpc_desc.rb:62:in `call'
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/rpc_desc.rb:62:in `block in unmarshal_proc'
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/active_call.rb:231:in `remote_read'
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/active_call.rb:309:in `request_response'
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/client_stub.rb:167:in `request_response'
/app/vendor/bundle/ruby/2.3.0/gems/grpc-1.0.0.pre1-x86_64-linux/src/ruby/lib/grpc/generic/service.rb:184:in `block (3 levels) in rpc_stub_class'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/datastore/service.rb:76:in `block in lookup'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/datastore/service.rb:144:in `block in execute'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/backoff.rb:112:in `block in execute_grpc'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/backoff.rb:110:in `loop'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/backoff.rb:110:in `execute_grpc'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/datastore/service.rb:143:in `execute'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/datastore/service.rb:76:in `lookup'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/datastore/dataset.rb:337:in `find_all'
/app/vendor/bundle/ruby/2.3.0/gems/gcloud-0.12.1/lib/gcloud/datastore/dataset.rb:306:in `find'

Probably it is more gcloud bug than grpc’s one (https://github.com/grpc/grpc/issues/7661)