Hey, thanks again but it seems that the parser doesn't recognize the key:
0(26767) CRITICAL: <core> [core/cfg.y:3434]: yyerror_at(): parse error in config file /etc/kamailio/kamailio.cfg, line 45, column 16: syntax error
0(26767) CRITICAL: <core> [core/cfg.y:3434]: yyerror_at(): parse error in config file /etc/kamailio/kamailio.cfg, line 45, column 16: unknown config variable 0(26767) CRITICAL: <core> [core/cfg.y:3434]: yyerror_at(): parse error in config file /etc/kamailio/kamailio.cfg, line 45, column 17: ERROR: bad config file (3 errors)