Image Caption not available in Import Feed?

Hi! I have a node with custom fields (using Fields UI). I have a multi-image uploader so that we can add as many images as we’d like, and for each provide an alt, title, and caption.
https://www.dropbox.com/s/d1r6gctdn5ltst1/field%20image%20setting%200.PN…

I did this by enabling a Caption field:
https://www.dropbox.com/s/joyr2860kefoh1z/field%20image%20setting%201.PN…

I can add these just fine, and they appear in my node just fine.

However, I’m importing mass content using the Import tool. I can choose which fields in my importing document go to which fields in my node. It seems all the fields are listed except the caption.
https://www.dropbox.com/s/cmem8dhxq6icmnl/field-image-setting-2.png?dl=0

Why? Where is that? How do I get my importer to add to the caption field?

Thanks,
Brendan

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/22/feed