diff --git a/README.md b/README.md
index a8bbd0800..d03e744fc 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@
 - gir1.2-gtk-3.0 (>=3.22)
 - python3-nbxmpp
 - python3-openssl (>=0.14)
+- python3-cssutils (>=1.0.2)
 
 
 ### Optional Runtime Requirements