diff --git a/release/cloudbuild-delete-canary.yaml b/release/cloudbuild-delete-canary.yaml
new file mode 100644
index 000000000..3589328f3
--- /dev/null
+++ b/release/cloudbuild-delete-canary.yaml
@@ -0,0 +1,46 @@
+# This will delete canary GAE versions named "nomulus".
+#
+# For reasons unknown, Spinnaker occasionally gets stuck when deploying to GAE
+# canary, and the fix is to manually delete the canary versions before the
+# deployment.
+#
+# To manually trigger a build on GCB, run:
+# gcloud builds submit --config=cloudbuild-delete-canary.yaml \
+# --substitutions=_ENV=[ENV] ..
+#
+# To trigger a build automatically, follow the instructions below and add a trigger:
+# https://cloud.google.com/cloud-build/docs/running-builds/automate-builds
+#
+steps:
+# Pull the credential for nomulus tool.
+- name: 'gcr.io/$PROJECT_ID/builder:latest'
+  entrypoint: /bin/bash
+  args:
+  - -c
+  - |
+    set -e
+    gcloud secrets versions access latest \
+      --secret nomulus-tool-cloudbuild-credential > tool-credential.json
+# Delete unused GAE versions.
+- name: 'gcr.io/$PROJECT_ID/builder:latest'
+  entrypoint: /bin/bash
+  args:
+  - -c
+  - |
+    if [ ${_ENV} == production ]
+    then
+      project_id="domain-registry"
+    else
+      project_id="domain-registry-${_ENV}"
+    fi
+
+    gcloud auth activate-service-account --key-file=tool-credential.json
+
+    for service in default pubapi backend bsa tools console
+    do
+      gcloud app versions delete nomulus --service=$service \
+        --project=$project_id --quiet;
+    done
+timeout: 3600s
+options:
+  machineType: 'N1_HIGHCPU_8'
diff --git a/release/cloudbuild-release.yaml b/release/cloudbuild-release.yaml
index 93975e112..3dc8e7071 100644
--- a/release/cloudbuild-release.yaml
+++ b/release/cloudbuild-release.yaml
@@ -88,6 +88,7 @@ steps:
     sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-schema-deploy.yaml
     sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-schema-verify.yaml
     sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-delete.yaml
+    sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-delete-canary.yaml
     sed -i s/builder:latest/builder@$builder_digest/g release/cloudbuild-restart-proxies.yaml
     sed -i s/GCP_PROJECT/${PROJECT_ID}/ proxy/kubernetes/proxy-*.yaml
     sed -i s/'$${TAG_NAME}'/${TAG_NAME}/g release/cloudbuild-sync-and-tag.yaml
@@ -100,6 +101,8 @@ steps:
         > release/cloudbuild-deploy-gke-${environment}.yaml
       sed s/'$${_ENV}'/${environment}/g release/cloudbuild-delete.yaml \
         > release/cloudbuild-delete-${environment}.yaml
+      sed s/'$${_ENV}'/${environment}/g release/cloudbuild-delete-canary.yaml \
+        > release/cloudbuild-delete-canary-${environment}.yaml
       sed s/'$${_ENV}'/${environment}/g release/cloudbuild-restart-proxies.yaml \
         > release/cloudbuild-restart-proxies-${environment}.yaml
       sed s/'$${_ENV}'/${environment}/g release/cloudbuild-restart-proxies.yaml | \