Fixes #949 (#968)

sass/utilities/derived-variables.sass

@@ -78,4 +78,4 @@ $size-large: $size-4 !default
 $colors: ("white": ($white, $black), "black": ($black, $white), "light": ($light, $light-invert), "dark": ($dark, $dark-invert), "primary": ($primary, $primary-invert), "info": ($info, $info-invert), "success": ($success, $success-invert), "warning": ($warning, $warning-invert), "danger": ($danger, $danger-invert)) !default
 $shades: ("black-bis": $black-bis, "black-ter": $black-ter, "grey-darker": $grey-darker, "grey-dark": $grey-dark, "grey": $grey, "grey-light": $grey-light, "grey-lighter": $grey-lighter, "white-ter": $white-ter, "white-bis": $white-bis) !default
 
-$sizes: $size-1 $size-2 $size-3 $size-4 $size-5 $size-6 !default
+$sizes: $size-1 $size-2 $size-3 $size-4 $size-5 $size-6 $size-7 !default

sass/utilities/variables.sass

@@ -147,4 +147,4 @@ $size-large: $size-4 !default
 
 $colors: ("white": ($white, $black), "black": ($black, $white), "light": ($light, $light-invert), "dark": ($dark, $dark-invert), "primary": ($primary, $primary-invert), "info": ($info, $info-invert), "success": ($success, $success-invert), "warning": ($warning, $warning-invert), "danger": ($danger, $danger-invert)) !default
 
-$sizes: $size-1 $size-2 $size-3 $size-4 $size-5 $size-6 !default
+$sizes: $size-1 $size-2 $size-3 $size-4 $size-5 $size-6 $size-7 !default