nginx: [emerg] "proxy_pass" cannot have URI part in location given by regular expression, or inside named location, or inside "if" statement, or inside "limit_except" block in /etc/nginx/includes/error-pages.conf:7

Hi I got this error:

nginx: [emerg] "proxy_pass" cannot have URI part in location given by regular expression, or inside named location, or inside "if" statement, or inside "limit_except" block in /etc/nginx/includes/error-pages.conf:7

My /error-pages.conf:

# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
error_page 404 = @fallback;

location @fallback {
proxy_pass https://aebian.org/404;
}





## Whats causing this?