xmlns:local="clr-namespace" serialized without assembly name

Hi I have problem with xmlns:local. 

I need to reference an activity in the same assembly

when I add activity from toolbox its add this in xaml file

xmlns:local="clr-namespace:XXX.Workflow.Activities"

but in this caseI need it to be 

xmlns:local="clr-namespace:XXX.Workflow.Activities;assembly=XXX.Workflow"

If I changed this manualy I loose it evrytime when xaml file has changed.

Any idea how to do that?