diff --git a/tools/rsync/api.go b/tools/rsync/api.go
index 4fd776f6a..a85b36abd 100644
--- a/tools/rsync/api.go
+++ b/tools/rsync/api.go
@@ -14,7 +14,7 @@ import (
 
 var _ = fmt.Print
 
-const MaxBlockSize int = 256 * 1024
+const MaxBlockSize int = 1024 * 1024 // sqrt of 1TB
 
 type StrongHashType uint16
 type WeakHashType uint16