diff --git a/HACKING.rst b/HACKING.rst
index 975498a01..b7e2564d6 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -179,3 +179,18 @@ without the patch and passes with the patch.
 
 For more information on creating unit tests and utilizing the testing
 infrastructure in OpenStack Nova, please read nova/testing/README.rst.
+
+
+openstack-common
+----------------
+
+A number of modules from openstack-common are imported into the project.
+
+These modules are "incubating" in openstack-common and are kept in sync
+with the help of openstack-common's update.py script. See:
+
+  http://wiki.openstack.org/CommonLibrary#Incubation
+
+The copy of the code should never be directly modified here. Please
+always update openstack-common first and then run the script to copy
+the changes across.