diff --git a/README.md b/README.md
index f7879ba64..cd5f9f39a 100644
--- a/README.md
+++ b/README.md
@@ -12,8 +12,9 @@ Compilation into HTML
 To compile this documentation :
 
 1. Install [sphinx-doc](http://sphinx-doc.org) (eg. pip install sphinx &  pip install sphinx_rtd_theme)
-2. run `make html` from the root directory
-3. The base file is located on build/html/index.html
+2. Install submodules : $ git submodule update --init;
+3. run `make html` from the root directory
+4. The base file is located on build/html/index.html
 
 Contribute
 ===========