diff --git a/public/v4/apps/maildev.yml b/public/v4/apps/maildev.yml
index 71671136b..f99261422 100644
--- a/public/v4/apps/maildev.yml
+++ b/public/v4/apps/maildev.yml
@@ -12,7 +12,7 @@ services:
             MAILDEV_MAIL_DIRECTORY: /data
             MAILDEV_WEB_USER: $$cap_maildev_web_user
             MAILDEV_WEB_PASS: $$cap_maildev_web_pass
-            MAILDEV_IP: ::
+            MAILDEV_IP: '::'
         caproverExtra:
             containerHttpPort: '1080'
 caproverOneClickApp: