Can custom elements' attributes be camelCased?

I have a custom element with attributes:

class MyElement extends HTMLElement {
    ...
    static get observedAttributes() {
        return ["camelCaseAttribute"];
    }

    set camelCaseAttribute(a) {
        this._a = a;
    }
    ...
 }

I use it in my HTML like so:

<my-element camelCaseAttribute="blubb"></my-element>

The attribute camelCaseAttribute is not set when writing it in camelCase, but writing it without upper-case-letters works. Why?