How do I keep semicolons in a serialized textarea?

I’m trying to hack ACF plugin until I get a response but I don’t even know where to start looking.

It seems wordpress is stripping the semicolons to prevent the serialization to break… or something else, but I bet ACF plugin is relying on it.

Specifically they are fontawesome characters (high numbers) that I want to be displayed inside a select box (the font doesn’t render in a drop-down select) and despite the semicolons are not rendered, the browser fixes most of them (the lower numbers) but the last third of icons render as a square.

I tracked the issue to the semicolon stripped from e.g. &#x f116; at some point, becoming &#xf116 (stripped semicolon)

I’ve read before something like “allowed characters”, but I can’t find it anymore ??

Thanks.