1 files changed, 1 insertions, 0 deletions

diff --git a/setup.cfg b/setup.cfg
index 8721816..c60f148 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -51,6 +51,7 @@ etcd =
 etcd3 =
   etcd3>=0.12.0 # Apache-2.0
   grpcio>=1.18.0
+  protobuf<4.0 # BSD License (3 clause)
 etcd3gw =
   etcd3gw!=0.2.6,>=0.1.0 # Apache-2.0
 zake =