diff --git a/docker-compose.ci.yml b/docker-compose.ci.yml
index 8568450..1a9d98b 100644
--- a/docker-compose.ci.yml
+++ b/docker-compose.ci.yml
@@ -43,10 +43,9 @@ services:
       #
       # Labels are baked into `./data/.runner` at registration — changing this
       # line later does nothing on its own. See the guide.
-      GITEA_RUNNER_LABELS: >-
-        ubuntu-latest:docker://catthehacker/ubuntu:act-24.04,
-        ubuntu-24.04:docker://catthehacker/ubuntu:act-24.04,
-        ubuntu-22.04:docker://catthehacker/ubuntu:act-22.04
+      # One line, no spaces after the commas: act_runner splits this on `,` and
+      # a stray space becomes part of the next label's name.
+      GITEA_RUNNER_LABELS: "ubuntu-latest:docker://catthehacker/ubuntu:act-24.04,ubuntu-24.04:docker://catthehacker/ubuntu:act-24.04,ubuntu-22.04:docker://catthehacker/ubuntu:act-22.04"
       CONFIG_FILE: /config/config.yaml
 
     volumes: