adding additional scan_listener port

I'm trying to see if we can add an additional port to the scan_listener or if this even possible ? This is for 11.2.0.3 on redhat 5.7.

I tried to add port 1525 to the scan_listener but got the following error below. (I've configured the two local listeners, one to listen to port 1521 and another to port 1525).

   

[grid@eaoalabtest09 tmp]$ srvctl modify scan_listener -p "TCP:1521/TCP:1525"
PRCS-1035 : Invalid number of TCP ports (2) for SCAN Listener