[syslog-ng] Changing message priority

Hi, I am trying to use rewrite to change a message's PRIORITY.  I am able to change the HOST to "info" using:   rewrite r_rewrite_set{set("info", value("HOST") condition(filter(f_logstash)));}; But, when I try setting the PRIORITY to "info", using this:   rewrite r_rewrite_set{set("info", value("PRIORITY") condition(filter(f_logstash)));}; But, when I try setting the PRIORITY to "info", using this: Error parsing rewrite expression, syntax error, unexpected LL_NUMBER, expecting LL_IDENTIFIER or LL_STRING in /etc/syslog-ng/f_messages.conf at line 8, column 27:included from /etc/syslog-ng.conf line 18, column 34rewrite r_rewrite_set{set(3, value("PRIORITY") condition(filter(f_logstash)));};^ Please advise on how I can fix this. Thanks.