Не могу установить расширение mbstring

При установке phpunit через composer получаю следующую ошибку

Your requirements could not be resolved to an installable set of packages.

Problem 1 - phpunit/phpunit 7.5.1 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system. - phpunit/phpunit 7.5.0 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system. - Installation request for phpunit/phpunit ^7.5 -> satisfiable by phpunit/phpunit[7.5.0, 7.5.1].

To enable extensions, verify that they are enabled in your .ini files: - /etc/php/7.3/cli/php.ini - /etc/php/7.3/cli/conf.d/10-opcache.ini - /etc/php/7.3/cli/conf.d/10-pdo.ini - /etc/php/7.3/cli/conf.d/15-xml.ini - /etc/php/7.3/cli/conf.d/20-calendar.ini - /etc/php/7.3/cli/conf.d/20-ctype.ini - /etc/php/7.3/cli/conf.d/20-curl.ini - /etc/php/7.3/cli/conf.d/20-dom.ini - /etc/php/7.3/cli/conf.d/20-exif.ini - /etc/php/7.3/cli/conf.d/20-fileinfo.ini - /etc/php/7.3/cli/conf.d/20-ftp.ini - /etc/php/7.3/cli/conf.d/20-gettext.ini - /etc/php/7.3/cli/conf.d/20-iconv.ini - /etc/php/7.3/cli/conf.d/20-json.ini - /etc/php/7.3/cli/conf.d/20-phar.ini - /etc/php/7.3/cli/conf.d/20-posix.ini - /etc/php/7.3/cli/conf.d/20-readline.ini - /etc/php/7.3/cli/conf.d/20-shmop.ini - /etc/php/7.3/cli/conf.d/20-simplexml.ini - /etc/php/7.3/cli/conf.d/20-sockets.ini - /etc/php/7.3/cli/conf.d/20-sysvmsg.ini - /etc/php/7.3/cli/conf.d/20-sysvsem.ini - /etc/php/7.3/cli/conf.d/20-sysvshm.ini - /etc/php/7.3/cli/conf.d/20-tokenizer.ini - /etc/php/7.3/cli/conf.d/20-wddx.ini - /etc/php/7.3/cli/conf.d/20-xdebug.ini - /etc/php/7.3/cli/conf.d/20-xmlreader.ini - /etc/php/7.3/cli/conf.d/20-xmlwriter.ini - /etc/php/7.3/cli/conf.d/20-xsl.ini You can also run php --ini inside terminal to see which files are used by PHP in CLI mode.

Installation failed, reverting ./composer.json to its original content.

Команда php -m показывает что расширение не подгружается Установил php-mbstring но ошибка та же. У кого есть идеи?