Почему мой селектор jQuery не может найти мой элемент по идентификатору?

I have a code with a simple jQuery selector usage:

$("label").each(function () {
    var target = $("#" + $(this).attr("for"));
});

I'm using PrimeFaces, so the HTML looks like:

<label for="j_idt23:txtNumber">Number:</label>
<input id="j_idt23:txtNumber" name="j_idt23:txtNumber" type="text" value="0" class="ui-inputfield ui-widget ui-state-default ui-corner-all" />

But it raises an error: "Syntax error, unrecognized expression: txtNumber".

What I'm doing wrong?