nominatim: Failed opening required ‘CONST_LibDir/init-website.php’ after installation

Hi. I followed the installation instructions with a fresh debian 11. php version is 7.4.21. Here is my apache configuration:

<VirtualHost *:80>
    ServerName geo.domain.tld

    <Directory "/usr/local/lib/nominatim/lib-php/website/">
        Options FollowSymLinks MultiViews
        AddType text/html   .php
        DirectoryIndex search.php
        Require all granted
    </Directory>

    DocumentRoot /usr/local/lib/nominatim/lib-php/website/
</VirtualHost>

Here is the error log generated when trying to access the domain:

[Thu Aug 19 14:26:42.482410 2021] [php7:warn] [pid 438204] [client ::1:34376] PHP Warning:  Use of undefined constant CONST_LibDir - assumed 'CONST_LibDir' (this will throw an Error in a future version of PHP) in /usr/local/lib/nominatim/lib-php/website/search.php on line 3
[Thu Aug 19 14:26:42.482778 2021] [php7:warn] [pid 438204] [client ::1:34376] PHP Warning:  require_once(CONST_LibDir/init-website.php): failed to open stream: No such file or directory in /usr/local/lib/nominatim/lib-php/website/search.php on line 3
[Thu Aug 19 14:26:42.482792 2021] [php7:error] [pid 438204] [client ::1:34376] PHP Fatal error:  require_once(): Failed opening required 'CONST_LibDir/init-website.php' (include_path='.:/usr/share/php') in /usr/local/lib/nominatim/lib-php/website/search.php on line 3

Is there something wrong with my installation?