dashes in arguments to zabbix agent cause ZBX_NOTSUPPORTED error

I've got a bunch of tests that test multipath disks ( dm-2, dm-3, etc ) which have stopped working since upgrading to the 1.8 agent, the tests work fine for 1.6 agents.

This is on a 64 bit centos box.

UserParameter=custom.vfs.dev.write.sectors[*],cat /proc/diskstats | grep $1 | head -1 | awk '

'

1. ./zabbix_get -s server -k custom.vfs.dev.write.sectors[dm-3] ZBX_NOTSUPPORTED

1. ./zabbix_get -s server -k custom.vfs.dev.write.sectors[sda]
   138643176

I've tried this with some other tests as well, and it seems as soon as I add a - into the argument it fails. Note I can run the test from the command line ( cat /proc/diskstats | grep dm-3 | head -1 | awk '

' ) and it works correctly.