anchor.diff:        };
   
         voiceIP = mkOption {
  -        type = types.str;
  -        default = "0.0.0.0";
  +        type = types.nullOr types.str;
  +        default = null;
  +        example = "0.0.0.0";
           description = ''
             IP on which the server instance will listen for incoming voice connections. Defaults to any IP.
           '';
  
positive.code:       };
  
        queryIP = mkOption {
          type = types.str;
          default = "0.0.0.0";
          description = ''
            IP on which the server instance will listen for incoming ServerQuery connections. Defaults to any IP.
          '';
  
negative.code:         ExecStart = ''
            ${ts3}/bin/ts3server \
              dbsqlpath=${ts3}/lib/teamspeak/sql/ logpath=${cfg.logPath} \
              ${optionalString (cfg.voiceIP != null) "voice_ip=${cfg.voiceIP}"} \
              default_voice_port=${toString cfg.defaultVoicePort} \
              ${optionalString (cfg.fileTransferIP != null) "filetransfer_ip=${cfg.fileTransferIP}"} \
              filetransfer_port=${toString cfg.fileTransferPort} \
              ${optionalString (cfg.queryIP != null) "query_ip=${cfg.queryIP}"} \
              query_port=${toString cfg.queryPort} license_accepted=1
          '';
          WorkingDirectory = cfg.dataDir;
          User = user;
  