ParserError: while parsing a block collection

General
1 
$ cat docker-compose.yml
version: "3.8"
services:
    composer:
        image: composer
        volumes:
            - "${COMPOSER_HOME:-$HOME/.config/composer}":/tmp
$ docker-compose run --rm composer sh -c cd .dev             && export COMPOSER_VENDOR_DIR=/var/tmp/5434211wefbnv             && composer  req -vvv workaround/utilities             && composer  upd             && composer  rem workaround/utilities
ERROR: yaml.parser.ParserError: while parsing a block collection
  in "./docker-compose.yml", line 6, column 13
expected <block end>, but found '<scalar>'
  in "./docker-compose.yml", line 6, column 57

Why?