Customer as partner in purchase orders

Experts,

When I try to link a customer parnter function in an MM partner schema I get the following message:

Cannot use this partner role

Message no. CZ327

Diagnosis

The partner role types you can use in partner maintenance for the Vendor

Master, Purchasing, and Arrangements areas are limited to 'LI' (Vendor)

and 'PE' (HR Master Record), plus, in Retail Industry systems only, 'AP'

(Contact Person).

I understand from this that a customer is not allowed as partner in MM.

Is there any (standard!) way to overcome this? Functionally I need this link and this means I have to setup all customers also as vendor.

Thanks for the feedback!

Jan