diff --git a/arda/pron.py b/arda/pron.py
index 852ed86..83a988a 100644
--- a/arda/pron.py
+++ b/arda/pron.py
@@ -2,7 +2,7 @@
 
 
 def is_vowel(ch):
-    return ch.lower() in "aeiouyäëïöüÿáéíóúý"
+    return ch.lower() in "aeiouyäëïöüÿáéíóúýâêîôûŷ"
 
 
 def is_short_vowel(ch):
diff --git a/pron_test.rst b/pron_test.rst
index 855cdbd..f599616 100644
--- a/pron_test.rst
+++ b/pron_test.rst
@@ -27,6 +27,7 @@
 ...     "silivren",
 ...     "andúne",
 ...     "dûn",
+...     "Udûn",
 ... ]:
 ...     print(word, display_word(syllabify(word)))
 Isildur i.SIL.dur
@@ -55,3 +56,4 @@ Pelargir pe.LAR.gir
 silivren si.LIV.ren
 andúne an.DÚ.ne
 dûn DÛN
+Udûn U.dûn
\ No newline at end of file