Cannot bind string component parameter to YoutubePlayer widget

I am currently creating a component that pops up when the user wants to open a video link (instead of redirecting them to YouTube via the "Launch URL" action).

Among other things, the component has a string parameter videoURL. I would now like to use this parameter in the YoutubePlayer widget and bind it to "URL". However, the component parameter "videoURL" is grayed out.

Interestingly, I could use it in a normal TextWidget.

Any ideas where the problem might lie? Thanks in advance.