Why isn't my positioning mixin working in Stylus when it works with Sass?

I use a positioning Mixins for aligning my divs to the top or left or center of the page etc, it works fine with SCSS/Sass but for some reason it's behaving very strangely when I try to use Stylus.

If I include one Mixin it works fine but when I add in more Mixins below, it will default to another Mixin.

Example of my Mixin:

top()
   position absolute
   margin auto
   top 0
   right 0
   //bottom 0
   left 0

Editable demo of the buggy code

Some theories:

• It's combining my declarations?
• Stylus can't tell which Mixin I'm calling?

You're missing the mixin indicator -. This should work for you:

// this is the mixin I'm calling, it positions the div to the top   
-top()
    position: absolute
    margin: auto
    top: 0
    right: 0
    left: 0

// for some reason the div is defaulting to this mixin instead
-center()
    position: absolute
    margin: auto
    top: 0
    right: 0
    bottom: 0   
    left: 0

// if you comment this block out it will work normally, calling the top() mixin only
-left()
    position: absolute
    margin: auto
    top: 0
    bottom: 0
    left: 0

// my div calling top() 
.block
    -top()  
    background: #345
    width: 100px
    height: 100px