Status Change CRITICAL to unknown removes acknowledgement

Hi,

i have a problem with omd 3.2 labs edition / naemon core:

A CRITICAL service has been acknowledged. After the service goes in status UNKNOWN, the acknowledgement is removed and we receive emails for the service state.

Is there any way to prevent the removing of the acknowledgement after state change CRITICAL to UNKNOWN and UNKNOWN to CRITICAL?

Thanks,
Ralf