Units of displayed object size will resets to mm

Migrated from: https://bugs.launchpad.net/inkscape/+bug/1807118

Steps to reproduce:

In document settings, set "display units" to "in" (or any other unit).
Create an object
Set the unit for the size of objects to "in" as well.
Close and relaunch document

What happened?

The size-of-object unit is set back to "mm" again, whereas I think, inkscape should remember my choice.

Inkscape Version and Operating System:

Inkscape Version: 1.0alpha (d7d7b92)
Operating System: Windows 10
Operating System version: 1803

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