Member -> New membership -> selecting priceset gives error: select at least one membership option

If I select "Membership -> New Membership"
And from this dialog; I do:
1. enter a name for a contact
2. Leaving "Membership organization" to default
3. Leaving "Membership type" to default
4. Selecting from "Priceset"

The price set fields appear, and "Membership type" + "Membership organization disappear

If I have a price set which include "quantity"; than I have a possibility to add the number I want, and the "Total" is updated correctly.

But when I click on [SAVE] button, an error appear:
----------------- below here is the error --------------------------
Please correct the following errors in the form fields below:

Select at least one membership option.
----------------- end of error ----------------------------------------