diff --git a/debian/postinst b/debian/postinst
index 3a53e686..489cf6ac 100644
--- a/debian/postinst
+++ b/debian/postinst
@@ -48,6 +48,16 @@ case "$1" in
 			true
 		fi
 
+		if dpkg --compare-versions "$2" 'lt' '2.3.1~'; then
+			lock_user="$(stat --format '%U' /etc/proxmox-backup/.datastore.lck)"
+			if [ "${lock_user}" != "backup" ]; then
+				echo "updating /etc/proxmox-backup/.datastore.lck from wrong user '${lock_user}' to 'backup'"
+				chown backup:backup /etc/proxmox-backup/.datastore.lck \
+				    || printf "Failed to fix datastore.lck user, please retry manually with:\n\n\t%s\n\n" \
+				        "chown backup:backup /etc/proxmox-backup/.datastore.lck"
+			fi
+		fi
+
 		if dpkg --compare-versions "$2" 'lt' '2.1.3~' && test -e /etc/proxmox-backup/sync.cfg; then
 			prev_job=""