diff --git a/api/sync15/common.go b/api/sync15/common.go
index c73358b..2ed7457 100644
--- a/api/sync15/common.go
+++ b/api/sync15/common.go
@@ -41,7 +41,7 @@ func getCachedTreePath() (string, error) {
 	return cacheFile, nil
 }
 
-const cacheVersion = 2
+const cacheVersion = 3
 
 func loadTree() (*HashTree, error) {
 	cacheFile, err := getCachedTreePath()
diff --git a/api/sync15/tree.go b/api/sync15/tree.go
index 2d6b251..3889c43 100644
--- a/api/sync15/tree.go
+++ b/api/sync15/tree.go
@@ -212,8 +212,9 @@ func (t *HashTree) Mirror(r RemoteStorage, maxconcurrent int) error {
 			if entry.Hash != doc.Hash {
 				log.Info.Println("doc updated: ", doc.DocumentID)
 				e := entry
+				d := doc
 				wg.Go(func() error {
-					return doc.Mirror(e, r)
+					return d.Mirror(e, r)
 				})
 			}
 		}