diff --git a/builders/testdata/python/appengine_sdk/requirements.txt b/builders/testdata/python/appengine_sdk/requirements.txt
index 2530063cf..cbc879fe9 100644
--- a/builders/testdata/python/appengine_sdk/requirements.txt
+++ b/builders/testdata/python/appengine_sdk/requirements.txt
@@ -1,2 +1,3 @@
 appengine-python-standard
 flask==1.1.1
+protobuf>=4.25.8 # not directly required, pinned by Snyk to avoid a vulnerability