diff --git a/git_test.go b/git_test.go
index 58caf71..6a58844 100644
--- a/git_test.go
+++ b/git_test.go
@@ -58,6 +58,8 @@
 	checkFatal(t, err)
 	err = idx.AddByPath("README")
 	checkFatal(t, err)
+	err = idx.Write()
+	checkFatal(t, err)
 	treeId, err := idx.WriteTree()
 	checkFatal(t, err)
 
@@ -91,6 +93,8 @@
 	checkFatal(t, err)
 	err = idx.AddByPath("README")
 	checkFatal(t, err)
+	err = idx.Write()
+	checkFatal(t, err)
 	treeId, err := idx.WriteTree()
 	checkFatal(t, err)
 
diff --git a/vendor/libgit2 b/vendor/libgit2
index 1dc4491..73dab76 160000
--- a/vendor/libgit2
+++ b/vendor/libgit2
@@ -1 +1 @@
-Subproject commit 1dc449105b329ea4f8ea9982bc2da869d231c04a
+Subproject commit 73dab7692e780e1df96093a54854795428eb66b4