diff --git a/auto-dictionary.el b/auto-dictionary.el
index 6cdc7c6..1c4b5f9 100644
--- a/auto-dictionary.el
+++ b/auto-dictionary.el
@@ -137,7 +137,7 @@ This is called when `auto-dictionary-mode' changes its mind or
           '(("en" "english")
             ("de" "deutsch" "german")
             ("fr" "francais" "french")
-            ("es" "español" "spanish")
+            ("es" "español" "spanish" "castellano")
             ("sv" "svenska" "swedish")
             ("sl" "slovenian" "slovene")
             ("hu" "magyar" "hungarian")