Comment 9 for bug 165952

I can confirm the problem, and it also applies to other
image file types.

JonCruz explained that it's to do with the fact that the
GTK+ loader does not preserve DPI.

However there is a fairly simple work around - import the
image, and adjust the size and measurement units in the
toolbar - and be sure to click on the lock first to preserve
aspect ratio.

- kattekrab