diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d3b7ad25c..2a78c3b1b 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -20,6 +20,15 @@ frustration later on.
 All submissions, including submissions by project members, require review. We
 use Github pull requests for this purpose.
 
+### Code style
+Before submitting a pull request make sure to run:
+
+	make pretty
+	
+This will format the source code according to the OpenThread code style. This
+command requires the `astyle` tool. Please refer to your operating system 
+documentation to find information on how to install `astyle`.
+
 ### The small print
 Contributions made by corporations are covered by a different agreement than
 the one above, the