Gender being changed to “Directory server” on Google Contacts insert

Question

I'm using the gdata-python-client library (http://code.google.com/p/gdata-python-client/) to insert contacts into a Google account. When I set the gender like this:

google_contact.gender = gdata.contacts.data.Gender(text="Male")

it's actually being set on the contact in the field "Directory server".

Any ideas why this might be happening?

In case it affects anything, my code is running on a Google App Engine development server.