cssnano conflicts with autoprefixer

[beldevel]

If we leave cssnano plugin as is, it will use it's own autoprefixer plugin which:

Removes unnecessary prefixes based on the browsers option. Note that by default, it will not add new prefixes to the CSS file. link

So, the autoprefixer which is used before cssnano comes out with distorted output.
In my case I needed display: -webkit-flex for older safari browsers but cssnano was just droppping it.
Disabling cssnano's autoprefixer fixes this issue: $.cssnano({ autoprefixer: false })

[bermanboris]

I'm experiencing this problem as well.

@beldevel solution solves the problem. Not sure if that's the correct way though.

gulpfile.babel.js

replace:
.pipe($.if('*.css', $.cssnano()))

with:
.pipe($.if('*.css', $.cssnano({autoprefixer: false})))