Narrowing occurred during type inference PHP 7.1 Warning

Been getting this warjning all over my error logs

"PHP message: PHP Warning:  Narrowing occurred during type inference. 
Please file a bug report on bugs.php.net in 
/srv/www/example.com/releases/20170922212452/web/wp/wp-settings.php on line 303" 
while reading response header from upstream, 
server: example.com, request: "GET / HTTP/2.0", 
upstream: "fastcgi://unix:/var/run/php-fpm-wordpress.sock:", 

the bug has been reported here: https://bugs.php.net/bug.php?id=74980 .
How can I update PHP to remove this warning?

I could be wrong but it seems like it got fixed in PHP 7.2 beta, so doesn’t seem like it’s released yet.