diff --git a/README.org b/README.org
index 184b50b..a03592f 100644
--- a/README.org
+++ b/README.org
@@ -2206,6 +2206,7 @@ list detailing and motivating each listing:
      ;; Beware: Python activation must not call still unbound functions.
      (python . t)
      (racket . ,(fboundp 'racket-mode))
+     (ruby . ,(fboundp 'ruby-mode))
      ;; MIT/GNU Scheme breaks Babel contrary to Guile, Chez and Chicken Scheme.
      (scheme . ,(fboundp 'geiser-mode))
      (shell . t))