diff --git a/subtree/README.md b/subtree/README.md
index 337e2c6b0..9c3df6609 100644
--- a/subtree/README.md
+++ b/subtree/README.md
@@ -1 +1,5 @@
-This folder contains git subtree projects of xgboost
+This folder contains git subtree projects of xgboost.
+Do not make changes to the subtree projects in xgboost,
+push changes to the original project instead and changes will be pulled back to this folder
+
+* rabit: https://github.com/tqchen/rabit