diff --git a/runner-config.yml b/runner-config.yml
index 3176071..9a7ef2f 100644
--- a/runner-config.yml
+++ b/runner-config.yml
@@ -17,5 +17,7 @@ container:
   privileged: false
   valid_volumes:
     - '**'
-  docker_host: "-"
+  # Auto-detect and mount the host docker socket into job containers so steps
+  # like "Update deploy.json" can `docker exec xetup-web`. ("-" disabled it.)
+  docker_host: ""
   force_pull: false