Unrecognized Database URL when using the docker image

[S0ulf3re]

I'm trying to use the notify_push image with my Nextcloud docker instance running on MariaDB. But when I set DATABASE_URL as using MariaDB, I just get an error about an unrecognized database URL. This is my config:

  notify_push:
    image: docker.io/icewind1991/notify_push
    container_name: notify_push
    networks:
      - mariadb
      - redis
      - nextcloud
    environment:
      - NEXTCLOUD_URL="https://nextcloud/"
      - REDIS_URL="redis://redis"
      - DATABASE_URL="mariadb://nextcloud:${NEXTCLOUD_MYSQL_PASSWORD}@db/nextcloud"
    depends_on:
      - db
      - redis
      - nextcloud

I've tried replacing the URI Scheme with mysql as well, but that didn't work either.