Bootstrap sass: set font size in em?

I have a responsive Bootstrap page with fixed size delimiters containing text. To avoid the div text overflow when resizing, I use this solution with media to change the default font size.

However, the variable $font-size-base

in Bootstrap sass variables is still defined in terms of pixels and so the stuff using it does not obey this scaling. I tried to change the font-base size to 1em

, but that causes a whole cascade of errors Incompatible units: 'px' and 'em'

.

I could basically overwrite the font sizes I have to be variable in in my custom sass file, but that seems like some sort of approach. Is there a cleaner way that Bootstrap can use ems for the font size so that it resizes to fit my media queries?