Presence of gender_id field on form results in freeform gender being set to integer

[ineffyble]

Context: Trying to get freeform gender up and running on our CiviCRM installation. For convenience, my plan is to keep the normal Gender select field, but have the freeform one appear if "Other" is selected (with a bit of JavaScript magic).

Problem: If I select "Other" and enter a value in the freeform gender field, upon submitting, my gender is set to "4", which is the ID of the "Other" gender option.