diff --git a/requirements.txt b/requirements.txt
index 92661a9..d5f56ed 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ pycryptodomex>=3.7.0
 requests>=2.9.1
 vdf>=3.3
 gevent>=1.3.0
-protobuf>=3.0.0
+protobuf>=3.0.0,<3.18.0
 gevent-eventemitter~=2.1
 cachetools>=3.0.0
 enum34==1.1.2; python_version < '3.4'