Source parameter not being entered from a leads.add call

I'm not seeing the "Source" being filled in when creating a lead with the leads.add call from my external website. Have tried using both the text label ("Website") and the numerical value (3) or the source select widget in the url (http://api.rentjuice.com/[api key]/leads.add.json?name=[name]&email=[email]&source=Website&etc.)

What gives?