Using Filters in Gateways for _env fields

I wonder if there is a problem configuring a filter on a gateway case the field to evaluate belongs to the _env structure.

I tried to configure a filter the following way:

startsWith(_env.trackId,“SOMESTRING”)

and it fails with the following message:

Filter Parse Error (205-1137): An unexpected character was encountered while parsing the filter.
line 1: startsWith(_env.trackId,"/T_NP_PHASEIII")
^
(BrokerFilter-7670)

Acording to the manuals this is the only way to reference a field on the envelope structure. (see bellow)

http://advantage.webmethods.com/bookshelf/Enterprise_APIs/Enterprise_APIs_V-4.1.1/EnterpriseServerReference-JavaPlatform-VolumeIv4.1.1.pdf

(page 65)

Note: When referring to envelope fields, you must add _env. to each of the field names shown in Table 14.

The above filter sintax is correct and apparently the problem lies on the underscore!!!

Did any of you have had this before?

I am running version 4.0.4 100402 of the broker server.