diff --git a/authorization/README.md b/authorization/README.md
index a7c73aa748a..55755685829 100644
--- a/authorization/README.md
+++ b/authorization/README.md
@@ -56,4 +56,6 @@ DEEPHAVEN_VERSION=${DEEPHAVEN_VERSION}  PATH=authorization-codegen:$PATH protoc
      $ROOT_DIR/health.proto
 
 ./gradlew :authorization:spotlessApply
-```
\ No newline at end of file
+```
+
+For protoc versions 3.12.x - 3.14.x, the `--experimental_allow_proto3_optional` flag is needed.