Remove a file in Amazon S3 using Django-storages

In my Django project I use Django-storageS to save media files in my Amazon S3.

I followed this tutorial (I use also Django-rest-framework). This works well for me: I can upload some images and I can see these on my S3 storage.

But, if I try to remove an instance of my model (that contains an ImageField) this not removes the corresponding file in S3. Is correct this? I need t remove also the resource in S3.