Taxonomy term form entity weights

When adding an entity reference field on a taxonomy vocabulary and using the inline entity form as widget the following occurs:

The flag '#ief_submit_all' is added to the containing forms submit button to trigger special inline entity form submit handlers. This is for example used for saving the weights of the different entities. On a node form, the provided form array is fully filled. On a taxonomy term node however, the provided form is not at all complete.

Adding of the flag fails, which in turn fails to save the weights of the entities. I'm not quite sure how to fix this. Changing the weight of module doesn't help. A temporary solution is to add a hook_form_alter in a custom module which add the flag for known vocabularies that use inline entity forms. This is not a longterm solution.

Any thoughts?