incorrect mixin support

[lazytyper]

Given code:

mixin a(option)
    if option 
        span if-branch
+a(true)

Expected result:

<?php if ( true ) ?><span>if-branch</span><?php else ?><span>else-branch</span>

Result:

<?php if ( option ) ?><span>if-branch</span><?php else ?><span>else-branch</span>

option isn't being replaced by true.