diff --git a/README b/README
index 171c76dc53..d47ea45671 100644
--- a/README
+++ b/README
@@ -122,6 +122,7 @@ REQUIREMENTS:
         libqrencode (optional)
         libmicrohttpd (optional)
         libpython (optional)
+        libidn (optional)
         gobject-introspection > 1.40.0 (optional)
         elfutils >= 158 (optional)
         make, gcc, and similar tools