diff --git a/README.rst b/README.rst
index 19bdf64..b7151c9 100644
--- a/README.rst
+++ b/README.rst
@@ -19,7 +19,8 @@ A Robot's Conundrom was created by Sakse Dalum, Niels G. W. Serup, and Lasse.
 Installation
 ============
 
-A Robot's Conundrum depends on PyGame <http://pygame.org>.
+A Robot's Conundrum depends on PyGame <http://pygame.org> and NumPy
+<https://numpy.org/>.
 
 The game can be run like this: