Kolab contact phone number labeled "Main" does not sync to an iPhone via ActiveSync

[kolab.user at use.startmail.com]

Create a new contact, add field "Organization" and type any name.
Add phone number under "Main" label, save contact.
Open connected via ActiveSync iPhone, search for newly added contact and observe that phone number is not present.

When connected via CardDav the same contact phone number is displayed but generic label "Phone" is used.