diff --git a/epitran/data/post/jpn-Hira.txt b/epitran/data/post/jpn-Hira.txt
index 82165be0..db435bfd 100644
--- a/epitran/data/post/jpn-Hira.txt
+++ b/epitran/data/post/jpn-Hira.txt
@@ -18,7 +18,7 @@ oo -> oː / _
 
 %Some special notations for long vowels
 ei -> eː / _
-ou -> oː / _
+oɯ -> oː / _
 
 % allophones of "[ら-ろ]" & "[りゃ-りょ]"
 ɾ -> ɖ / # _
diff --git a/epitran/data/post/jpn-Kana.txt b/epitran/data/post/jpn-Kana.txt
index 91698cfb..4a2ae650 100644
--- a/epitran/data/post/jpn-Kana.txt
+++ b/epitran/data/post/jpn-Kana.txt
@@ -18,7 +18,7 @@ oo -> oː / _
 
 %Some special notations for long vowels
 ei -> eː / _
-ou -> oː / _
+oɯ -> oː / _
 
 % allophones of "[ラ-ロ]" & "[リャ-リョ]"
 ɾ -> ɖ / # _
diff --git a/epitran/test/test_japanese.py b/epitran/test/test_japanese.py
new file mode 100644
index 00000000..1567952a
--- /dev/null
+++ b/epitran/test/test_japanese.py
@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import unicode_literals
+
+import unittest
+
+import epitran
+
+
+class TestJapanese(unittest.TestCase):
+    def setUp(self):
+        self.epi = epitran.Epitran(u'jpn-Hira')
+
+    def test_longvowels(self):
+        tr = self.epi.transliterate('とうきょう')
+        self.assertEqual(tr, 'toːkʲoː')