@supports (display: flex) is not prefixed

The result of gulp-autoprefixer on the following block

@supports (display: flex) {
  div {
     display: flex;
     /* ... */
  }
}

is

@supports (display: flex) {
  div {
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
    /* ... */
  }
}

So the display declaration is well prefixed but, if I’m not wrong, the @supports should be prefixed like this:

@supports (display: -webkit-box) or (display: -webkit-flex) or (display: -ms-flexbox) or (display: flex) {
  div {
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
    /* ... */
  }
}

Is it a bug ? Thank you in advance and sorry if I’m wrong.

[ai]

Yeap. Seems like we have a bug here. I will look at in on next week (sorry, preparing for conference)

[ghost]

Ok Andrey, I will do that.