diff --git a/requirements.txt b/requirements.txt
index ade9a108..5f651098 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,3 +4,6 @@ ops >= 2.2.0
 jinja2
 redfish
 git+https://github.com/canonical/prometheus-hardware-exporter.git
+# Keep protobuf < 4.0 until macaroonbakery solves its incompatibility
+# https://github.com/go-macaroon-bakery/py-macaroon-bakery/issues/94
+protobuf<4.0