Disable max-height for feed images

Hi!

I have set 'Compact UI' in the settings set to 'No - expand images' but in my home feed they are still cut off. Looking at the code I can see the following:

.post_teaser_image_preview a {  
    max-height: 575px;  
    overflow: hidden;  
}  

and disabling max-height solves my issue (seeing the whole image in the feed without clicking it).

How do I specify this in the custom CSS section in the settings so that the max-height is always disabled?
I tried

:disable {  
    .post_teaser_image_preview a {  
        max-height: 575px;  
    }  
}  

but it doesn't work.