GTK applications tooltips are unreadable within Plasma 5

I’m experiencing a little issue with GTK apps inside Plasma 5.

The tooltips use a color scheme (white text over light grey backround) that makes them unreadable, as you ca see from the screenshot

How can I solve this?

Known problem.

Try to use a different GTK theme, or maybe changing the setting “Apply colors to non-Qt applications” (in KDE’s settings->Colors) helps…