Spectrum viewer: changing x-scale after zoom results in blank screen

After zooming into a specific wavelength range (say 6500 Angstroms), then changing the wavelength units from angstroms to nanometers, the x-axis scale does not change automatically and the spectrum view is blank. You have to hit the rescale button to see the plot again.

This problem does not appear if you select a different wavelength unit with a full-scale spectrum (that is, without performing any zoom).