Places goes to great lengths to ensure all items have GUIDs, and has a "unique" index on the column. It has DEBUG-only code in Database::Shutdown() that asserts if it finds any NULL items, but best I can tell, this isn't actually enforced. Doing this would allow Sync to remove some complexity around ensuring items have GUIDs when best I can tell, that's already true, just not enforced. ISTM this might be as easy as changing the GUID column to be "NOT NULL"? Mak, is there something I'm missing here?