Setting up a free subscription in membership while using paypal express for paid memberships.

Hello, I just got done testing a full round trip using Paypal Express in the membership plugin for paid subscriptions, and it works like a dream. I have an issue with my free subscription, however. I only have Paypal Express set up in the membership plugin as the only gateway. I have 3 access levels ... visitor, free, and premium. I have all of the paid subscription options (monthly, yearly, and lifetime), and I have the one free subscription. While testing the site, I went through to the register page, and clicked on the free subscription. It brought me to the page where you click on the subscribe button, but when I click on it, the page just refreshes and when I check the members section in the plugin, the subscription is not added to the user. I set the price in the subscription section to 0.00, which is when it does not work, so I thought of trying to set it to 1.00, and as soon as I set the price from 0 to 1, the button brought me to Paypal in order to complete the registration. How do I get a free subscription, if I can't set price to 0.00?