diff --git a/requirements.txt b/requirements.txt
index d5f56ed..14293fb 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,8 @@ pycryptodomex>=3.7.0
 requests>=2.9.1
 vdf>=3.3
 gevent>=1.3.0
-protobuf>=3.0.0,<3.18.0
+protobuf>~3.0; python_version >= '3'
+protobuf<3.18.0; python_version < '3'
 gevent-eventemitter~=2.1
 cachetools>=3.0.0
 enum34==1.1.2; python_version < '3.4'