Text background color doesn't export from Impress into PDF

When I have some text in LibreOffice impress (Edit: also 5.3.0) and apply a color as “background” (called highlight in later version), this color will appear transparent in the PDF exported from there. Note that this does not occur with the “highlight color” in Writer.

Agree! It’s a problem. I checked it with Did you report a bug? Seems like a good idea.
But I noticed something interesting: the highlighting also disappears when you show full-screen (slideshow). So maybe it’s deliberate for some reason?

Still happens in Was this bug ever reported?