example for mixins from documentation doesn't work

[voidKandy]

mixin properties don't seem to work as advertised in the documentation. I copy-pasted the code from this page in the documentation, and the mixin seems to do nothing. The below code is my html page I'm trying to render, and I've installed assembler using the CDN.

  <style>
    :root {
      --stripes--mixin: "bg-color: slateblue; \
        bg-image:repeating-linear-gradient(45deg, white 0 3px, #0003 3px 9px)";
    }
  </style>
  <div x-style="^stripes; w:150px; h:150px; mx:auto; radius"></div>

I know assembler is working because the css associated with all the other values in the x-style attribute are being applied (w:150px; h:150px; etx.).

I've used Assembler for 3 sites now and I've never gotten mixins to work as advertised (or at all). Would love to get this working as I really enjoy using Assembler, and mixins would be a nice cherry on top.