Duplicate SVG attribute

[Paolo Prete]

Hello,

I'm noting that the generated SVG of this...:

{
    \once \override DynamicText.output-attributes.val = "x"
    \once \override DynamicText.output-attributes.val = "y"
    c'\mf
}

... creates the following SVG tag, with a duplicate "val" attribute:
<g val="y" val="x">

Is this a bug? Also note that the duplication doesn't happen if I use
"\override" instead of "\once \override".

In case of a bug, is there a workaround for it (I mean: is there a way to
call \once \override multiple times for the same attribute without
duplicating it)?

Thanks very much!
Paolo