Compressed jpg's uncompress on next "edit ebook"

[icaros]

I always compress images to keep epub filesize small. That works fine. However, the next time I select "edit ebook" Calibre goes and replaces the compressed image with the uncompressed calibre cover.jpg - without asking or giving me an option not to.

Is there a method to avoid this behaviour? I have tons of epubs and edit them a lot, so it often happens that I end up with a larger than wanted file.

Or is there a way to easily (automatically) have the compressed epub cover image to be used for the calibre cover.jpg?

win10 calibre 2.79

edit:
Can't find a way to delete this post. I found a setting in the "edit book" preferences under "integration" and untick "update metadata..."