wp_link_pages() errors

I’m using the function wp_link_pages() in my wordpress theme to make the page links for multi-paged posts and am coming up against an xhtml validation error. The html generated by the function is not encoding the & in the urls. E.g.
<a href="https://example.com?p=188&page=2">2</a> should be <a href="https://example.com?p=188&page=2">2</a>

edit: this forum seems to be unencoding even my coded & symbols. The 2nd example should have a &amp ; instead of a &. (without the space before the ??

Here is my code with the function arguments:

<?php wp_link_pages( array( 'before' => '<div class="page-link">' . __( 'Pages:', '' ), 'after' => '</div>' ) ); ?>

Any ideas as to how I can get it to make valid xhmtl?