diff --git a/.gitmodules b/.gitmodules
index 1b3eca1..adeb262 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -22,6 +22,7 @@
 [submodule "deps/protobuf"]
 	path = deps/protobuf
 	url = https://github.com/protocolbuffers/protobuf.git
+	branch = 3.20.x
 [submodule "deps/rapidjson"]
 	path = deps/rapidjson
 	url = https://github.com/Tencent/rapidjson.git