TinyMCE ‘fontsize_formats’ problems with rem since 4.9.6

Hi,

After updating wordpress to 4.9.6, I’ve got a problem with the hook tiny_mce_before_init.

I customize the font size I can use with the following code :

$args['fontsize_formats'] = ".25rem .5rem 1rem 1.125rem 1.25rem 1.5rem 1.625rem 1.75rem 2.125rem 2.25rem 2.5rem";

The list is replaced by these values, but only values ??less than 1rem work.
When a value between 1rem and 2rem is selected, the font-size is set to xx-small.
After 2rem, the font-size is set to x-small.

I tested other units like px or pt and it work, but rem seems to need a fix.

Thanks for your reply.