SASS - @mixin @media - How to adapt sass variables for tablets width?

Hello,

I know this doesn’t work because I declare variables in a mixin.

But do you know how to make that work ?

$tablet-width: 768px;

@mixin tablet {
  @media (min-width: #{$tablet-width})  {
    @content;
  }
}

@include tablet {
  $bar-height :               70px !default;
  $bar-subheader-height :     100px !default;
  $button-bar-button-height : 70px !default;
}