diff --git a/tools/c7n_mailer/requirements.txt b/tools/c7n_mailer/requirements.txt
index d7e47be6960..dcfae7fa619 100644
--- a/tools/c7n_mailer/requirements.txt
+++ b/tools/c7n_mailer/requirements.txt
@@ -11,3 +11,4 @@ datadog==0.28.0
 sendgrid==6.0.5
 redis==3.2.1
 ldap3==2.6
+zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability