diff --git a/images/kube-webhook-certgen/cloudbuild.yaml b/images/kube-webhook-certgen/cloudbuild.yaml
index 8282daf52..8bdd225c5 100644
--- a/images/kube-webhook-certgen/cloudbuild.yaml
+++ b/images/kube-webhook-certgen/cloudbuild.yaml
@@ -34,4 +34,4 @@ steps:
       && make push
 substitutions:
   _GIT_TAG: "12345"
-  _PULL_BASE_REF: "master"
\ No newline at end of file
+  _PULL_BASE_REF: "main"