diff --git a/README.md b/README.md
index 885178f..1d005b3 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,9 @@ You can move a NAO around using a "Human Joystick" approach and make NAO
 imitate your arm motions. For more details, read our
 ![report](docs/report.latex).
 
+Our package relies on the NAO being reachable from the computer and the
+environment variable `NAO_IP` being set to the IP address of the NAO.
+
 ## Requirements
 
 * ROS Indigo on Ubuntu 14.04