iRule Error related with Data Group

We need to block some User-Agent, so I created a Data Group that called UnwantedAgents, and an iRules called ir_BlockAgents

when HTTP_REQUEST { if { [class match [string tolower [HTTP::header "User-Agent"]] contains UnwantedAgents ] } { log local0. "Blocked src=[IP::client_addr] src_port=[TCP::client_port],agent= HTTP::header value User-Agent]" reject } }

After I applied this iRule ir_BlockAgents. I saw this error in the log (/var/log/ltm)

Feb 21 12:26:51 jcbigip1 err mcpd[5407]: 01020066:3: The requested rule (/Common/ir_BlockAgents) already exists in partition Common.

How can I fix it?

Thanks, Xin