[Docker Cloud] Labels on Services cause error in redeploy

If you try to put a Label on a Service you created before, it force a redeploy.
The issue is that this deploy will fails until you remove the label.
If this label should be intended as a reference for existing node for deploy, maybe a select-field should be used instead.
I understand it could also be useful having a reference to a node you will create after. But in that case a warning could be raised.
Also should be possible to choose the alternative behavior in case of a miss in node labels list.

It works well if the label match exactly a node label. So this is not an issue, maybe just not so easy to use.
Also, the error message is generic an doesn’t help so much to understand the wrong configuration that caused the failure in deploying.