Keychain Helper fails with "User interaction is not allowed" when user interaction is not needed

[indirect]

Reproduction steps:

1. ssh localhost
2. cd ~/src/bundler/bundler
3. git remote update

What happens:

$ git remote update
Boxen Keychain Helper: Encountered error code: -25308
Error: User interaction is not allowed.
Boxen Keychain Helper: Encountered error code: -25308
Error: User interaction is not allowed.
remote: Anonymous access to bundler/bundler.git denied.
fatal: Authentication failed for 'https://github.com/bundler/bundler.git/'

While user interaction may not be allowed, the keychain is unlocked, and security find-internet-password works perfectly fine even inside the ssh localhost.

What I expected to happen (and what does happen in a local terminal window, with no GUI prompts):

$ git remote update
etching origin
remote: Counting objects: 2, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 2 (delta 0), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (2/2), done.
From https://github.com/bundler/bundler
   2e3a267..4466cb4  master     -> origin/master