diff --git a/jjb/job-templates.yaml b/jjb/job-templates.yaml
index 823faa4e9a..25d4df00d1 100644
--- a/jjb/job-templates.yaml
+++ b/jjb/job-templates.yaml
@@ -70,6 +70,18 @@
     builders:
       - docker-castor-load
       - docker-src-dir
+
+      # Ensure /log files are writable before deleting - T320251
+      - shell: |
+          mkdir -m 2777 -p "log"
+      - docker-run:
+          image: docker-registry.wikimedia.org/buster:latest
+          entrypoint: /bin/chmod
+          options: >-
+              --volume "$WORKSPACE/log":/log
+          args: >-
+              -R u+w /log
+
       - docker-log-dir
       - docker-ci-src-setup-simple
       - docker-run-with-log-cache-src: