diff --git a/doc/install.rst b/doc/install.rst
index b27d39c..5f13583 100644
--- a/doc/install.rst
+++ b/doc/install.rst
@@ -33,6 +33,7 @@ Depending on how you are going to use PySAML2 you might also need
 * decorator
 * python-memcache
 * memcached
+* M2Crypto
 
 Quick build instructions
 ^^^^^^^^^^^^^^^^^^^^^^^^