diff --git a/.gitmodules b/.gitmodules
index 406c9695..307a0843 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,4 @@
 [submodule "vtm"]
 	path = vtm
 	url = git@github.com:xiaoyan159/vtm.git
+	branch = master
diff --git a/vtm b/vtm
deleted file mode 160000
index dd13e533..00000000
--- a/vtm
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit dd13e533c38b5738ab404c2737d7ccadeff01323