TS Strict config not working

[Sufiane]

I'm playing around with XO, and can't get away from the following error:

This rule requires the strictNullChecks compiler option to be turned on to function correctly. @typescript-eslint/prefer-nullish-coalescing

It should work out of the box since xo should handles as stated here

I even turned everything on in my own tsconfig.json, but w/o success.

Since I've seen in other issues that restarting your IDE (Webstorm in my case) may work I've done it. No success either.

Did I missed something ?