DeltaBlocks CSS hiding - setting won't save

I put my Branding in a region using the DeltaBlock.

In Settings for the block, I tick "Hide the site name via CSS" and save the form.

On the Blocks page, I still see the site name, and I look at the block settings again and the tick is gone. It's not possible to save that element of the form. Other settings on the form save fine, like block-name and page-display settings.

I'm working around it, having done variable_set('delta_blocks_branding_site_name_hidden', 1);