og_group_ref token being ignored

The problem

Files from a file field are not being uploaded to the path I configured using the og_group_ref token.

Info

I have set the File path pattern to:
groups/[node:og_group_ref]/post/[node:title]
Uploaded file paths look like:
http://localhost/system/files/groups/post/another%20file/test33.txt
That should be:
http://localhost/system/files/groups/<og_group_ref>/post/another%20file/test33.txt

Drupal does not output any errors. PHP does not log any errors either.

Pathauto creates the path alias using the group name correctly.

System info

Drupal 7.41.
PHP 5.5.
Linux Mint 17.2
Entity Token 7.x-1.6
Token 7.x-1.6

Any suggestions?