diff --git a/num2words/lang_ES.py b/num2words/lang_ES.py
index 18e6da5..6291fd7 100644
--- a/num2words/lang_ES.py
+++ b/num2words/lang_ES.py
@@ -363,4 +363,5 @@ class Num2Word_ES(Num2Word_EU):
                 list_result[0] = list_result[0].replace("uno", "una")
                 result = " ".join(list_result)
         result = result.replace("uno", "un")
+        result = result.replace("veintiun", "veintiún") # correct orthography for this specific case
         return result