deathday format destruction

eM Client nextcloud

When entering in nextcloud/contacts a deathdate, it will be saved as
DEATHDATE;VALUE=DATE:20190421
Now opening this contact in eM Client and adding e.g. a given name, eM client also will change the deathdate to
DEATHDATE;VALUE=time:000000
This is wrong. VALUE=DATE should be kept and the date 20190421 should not be touched.