.

go/zodb/storage/demo/demo.go

@@ -91,7 +91,9 @@ func (d *Storage) Sync(ctx context.Context) (_ zodb.Tid, err error) {
 		if err != nil {
 			return err
 		}
-		// XXX baseHead != .baseAt0 -> fail
+		if baseHead != d.baseAt0 {
+			return &baseMutatedError{d.baseAt0, baseHead}
+		}
 		return nil
 	})