How to enable DRM in firejail?

I would like to set browser-allow-drm yes for my librewolf profile. However, there is no Nixos option to do this globally and setting it in a local profile doesn’t work:

    librewolfjail = {
      executable = "${pkgs.lib.getBin pkgs.librewolf}/bin/librewolf";
      profile = pkgs.writeText "librewolf.local" ''
        noblacklist ''${DOWNLOADS}
        whitelist ''${DOWNLOADS}
        # Enable DRM 
        browser-allow-drm yes        
        ?BROWSER_ALLOW_DRM: ignore noexec ''${HOME}        
        include librewolf.profile

This yields Error: line 4 in /nix/store/i0awqmvmir9m3lxx491lxmxf6af93z42-librewolf.local is invalid and prevents librewolf from launching.

How do i set this option correctly?