How to type SubmitEvent so that event.target.children is known?

Question

I have the following form:

<form id="search" method="post">
<input type="text" name="query" id="search-field"/>
</form>

And I want to attach a submit event listener in TypeScript:

document.getElementById("search").addEventListener("submit", (event: SubmitEvent) => {
        event.preventDefault();
        console.log(event.target.children.query.value);
    });

However typescript gives me the following error:

error TS2339: Property 'children' does not exist on type 'EventTarget'.

20    console.log(event.target.children.query.value);

How can I tell TypeScript that the target of the submit event is a form, which has a valid children.query element?