squid-cache does not print local port number of the last server connection

Issue

We need to print on squid access.log information about local port number of the last server.
I added in squid.conf file the '%<lp' parameter as described in the documentation on the squid-cache site:
http://www.squid-cache.org/Versions/v3/3.1/cfgman/logformat.html

but we received the following message error trying to reload squid:

# service squid reload
FATAL: Can't parse configuration token: '%<lp %rm %ru %un %Sh/%<A %mt "%{User-Agent}>h" "%{Referer}>h"'

Squid Cache (Version 3.1.10): Terminated abnormally.
CPU Usage: 0.012 seconds = 0.009 user + 0.003 sys
Maximum Resident Size: 23056 KB
Page faults with physical i/o: 0

The logfomat string used was:

logformat squidmime %ts.%03tu %6tr %>a %Ss/%03>Hs %<st %<lp %rm %ru %un %Sh/%<A %mt "%{User-Agent}>h" "%{Referer}>h"