Idoc extension problem

Hi experts,

Im facing one problem, the scenario is 3rd party system -> PO 7.31 (JAVA stack only) -> HCM.

I extended just the structure of one standard segment, (in se11, not in we31) and when I send the idoc to HCM i dont receive the extended field...

In the operation mapping I used the idoc standard and in the Message Mapping I use as target an external definition with the field created manually.

I sow in the last step of the monitor, the message has the extended field. I dont know if the Idoc communication channel is the one who is removing this field or if is in the HCM backend.

Do anyone know how I can solve it? The purpose is not extend the idoc in we31

Thanks in advance.