It doesn't work with Entity Construction Kit (ECK)

Problem/Motivation

I was unable to get the module to work with entities created using the Entity Construction Kit (ECK) module.

Steps to reproduce

1. Install the Entity Construction Kit (ECK) module.
2. Create an entity type via ECK.
3. Create an ECK entity type bundle.
4. Enable the created entity type in the autosave settings.
5. Check the "Allowed for new entities" option in the autosave settings.
6. Go to the creation form of an entity from the previously created entity type bundle.