diff --git a/grpc/Makefile b/grpc/Makefile
index a67a935..d5e85fc 100644
--- a/grpc/Makefile
+++ b/grpc/Makefile
@@ -19,7 +19,6 @@ endif
 # generate api proto
 generate:
 	protoc --proto_path=./ \
-		   --experimental_allow_proto3_optional \
 	       --proto_path=./third_party \
  	       --go_out=paths=source_relative:./ \
  	       --go-http_out=paths=source_relative:./ \