diff --git a/requirements.txt b/requirements.txt
index a90e15c..4ece85d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,3 +5,4 @@ requests==2.20.1
 grpcio==1.15.0
 grpcio-tools==1.15.0
 grpcio-health-checking==1.15.0
+protobuf>=4.25.8 # not directly required, pinned by Snyk to avoid a vulnerability