Transparency Grid expands weirdly when using GPU

[hellopaul4]

If I'm using GPU acceleration, and turn on Transparency Grid in the Program viewer, the transparency grid is always scaled to "fit", regardless of what the zoom level actually is, like this:

If I switch to "software only" in the project settings, I get this, correct view:

I shall update my Nvidia drivers later - I'm currently on 551.52. 551.61 is the latest available driver.