[Ionic 4] Disable IE11 polyfill for css variables

Hi, I use Ionic 4 (for IE11 reasons) and I need to use css-variables, but in an async way : I am fetching css variables from a webservice, and then I need to apply them.

My problem: I can’t use this approach with Ionic 4, because it hard-replaces all my css-variables in IE11. So when I get my css variables, there are no variables left in my css code to be replaced.

I could not see any option to disable IE11 CSS Variable polyfill. Is there any? Or is there any other way I can solve async theming in ionic in IE11?