diff --git a/docker-compose.yml b/docker-compose.yml
index 7c8d943..3ad27ab 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -11,7 +11,7 @@ services:
       # Bearer token for POST /api/deploy. Set it in a .env file next to this
       # compose file (gitignored); the route returns 404 when it is unset.
       - DEPLOY_TRIGGER_SECRET=${DEPLOY_TRIGGER_SECRET:-}
-      - DEPLOY_TRIGGER_DIR=/deploy-trigger
+      - DEPLOY_TRIGGER_DIR=${DEPLOY_TRIGGER_DIR:-/deploy-trigger}
     volumes:
       # Shared with scripts/deploy-watch.sh on the host.
       - ./deploy-trigger:/deploy-trigger