WPF: Strange image stretching in Buttons

Question

I have multiple buttons, each having a 32x32 pixels PNG image. The strange thing is, that both buttons show different sizes (Yes, I triple checked that icons are really 32x32!).

Answer 1

To follow up on SLaks answer: To use the Pixel dimensions of the Image regardless of the DPI you can bind the Width and Height to the PixelWidth and PixelHeight of the Source like this