Attribute put in lowercase?

[real-felix]

I just hit a very confusing behavior. I was following this event example for Alpine JS https://alpinejs.dev/essentials/events#listening-for-events-on-window and I replaced foo with my own signal:

a "@click"="$dispatch('showLangDialog')" {
    span { "Language" }
}

div x-data="{ show: false }" x-cloak x-show="show"
    "@showLangDialog.window"="show = true"
{
    etc.
}

To my surprise, the attribute from the latter snippet became @showlangdialog.window="show = true" in lowercase, which breaks the signal transmission. If it's not by accident, what is the reason why it's put in lowercase?