diff --git a/README.md b/README.md
index 8451d0ea..9f86838d 100644
--- a/README.md
+++ b/README.md
@@ -210,6 +210,10 @@ process.
     idea). With Vundle, this would mean adding a `Bundle
     'Valloric/YouCompleteMe'` line to your [vimrc][].
 
+    If you don't install YCM with Vundle, make sure you have run
+    `git submodule update --init --recursive` after checking out the YCM
+    repository (Vundle will do this for you).
+
 3.  [Complete this step ONLY if you care about semantic completion support for
     C-family languages. Otherwise it's not neccessary.]