Fix compile error in HEAD
Fix compile error in HEAD

Summary:
- Changes doesn't seem to have run diff builds of my last change for some
  reason, and it had a compile error :|

Test Plan: This was green when I `arc beta-test`ed

Reviewers: kylec

Reviewed By: kylec

Subscribers: changesbot, anupc

Differential Revision: https://tails.corp.dropbox.com/D173891

dropbox/changes-client,dropbox/changes-client