v4 - Error: $color: 'theme-color("primary")' is not a color for `darken'

Created by: sjdeere

i have switch to v4 instead of the alphav6

npm install bootstrap@4.0.0-beta

and when i compile i get

Error: $color: 'theme-color("primary")' is not a color for `darken' on line 168 of sass/bootstrap/_variables.scss