force change units in mne read_raw_edf

Question

I'm trying to set the units of my eeg to microvolts when reading an edf file:

import mne

raw = mne.io.read_raw_edf('my_edf.edf', units='uV')

But I'm getting the following error:

ValueError: Unit for channel F4 is present in the file as 'mV', cannot overwrite it with the units argument 'uV'.

Now I don't really care what the edf says the unit is: I want to convert everything to microvolts. How do I do that?