diff --git a/weed/filer/filerstore.go b/weed/filer/filerstore.go
index 4b28c3021..5716f704c 100644
--- a/weed/filer/filerstore.go
+++ b/weed/filer/filerstore.go
@@ -16,6 +16,8 @@ var (
 	ErrUnsupportedListDirectoryPrefixed = errors.New("unsupported directory prefix listing")
 	ErrKvNotImplemented                 = errors.New("kv not implemented yet")
 	ErrKvNotFound                       = errors.New("kv: not found")
+
+	_ = VirtualFilerStore(&FilerStoreWrapper{})
 )
 
 type FilerStore interface {