diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index fdee288b..f7517a02 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -43,6 +43,10 @@ Submitting patches
 - Include tests if your patch is supposed to solve a bug, and explain
   clearly under which circumstances the bug happens. Make sure the test fails
   without your patch.
+- Include a string like "Fixes #123" in your commit message
+  (where 123 is the issue you fixed).
+  See `Closing issues using keywords
+  <https://help.github.com/articles/creating-a-pull-request/>`__.
 
 First time setup
 ~~~~~~~~~~~~~~~~