Custom WebApp & Typo3

I tried to modify the nginx conf file for one of my instances of WebApps by changing following value :

fastcgi_pass unix:/var/run/php/php7.2-fpm-my_webapp__8.sock;

However, when I try to reach the page, I get the following error: 502 Bad Gateway ; if I put the original configuration (7.0), Typo3’s installation service requires to update from PHP 7.0 to 7.2…