diff --git a/proto/README.md b/proto/README.md
index 79d320504d..31a0747ad8 100644
--- a/proto/README.md
+++ b/proto/README.md
@@ -10,6 +10,9 @@ Dependencies are git submodules in //proto/third_party. You need to build
 protoc in //proto/third_party/protobuf by running `bazel build //:protoc` from
 that directory. Currently tested with bazel version 0.28.0.
 
+You also need to run `go build -o ._protoc-gen-go ./protoc-gen-go` in
+third_party/golang-protobuf.
+
 Dependency tracking and hermeticity here poor.
 
 Generating code