diff --git a/tcii18n/translator.py b/tcii18n/translator.py
index d6ff9e9..5a3f4ee 100644
--- a/tcii18n/translator.py
+++ b/tcii18n/translator.py
@@ -13,3 +13,4 @@ def translate(self, sentence, **kwargs):
                 for key, value in kwargs.items():
                     row[1] = row[1] % {key: value}
                 return row[1]
+        return sentence
diff --git a/test/i18n.py b/test/i18n.py
index 3c0697d..877b03d 100644
--- a/test/i18n.py
+++ b/test/i18n.py
@@ -21,3 +21,6 @@ def test_switch_language(self):
         self.assertEqual(self.trans_it('TCI title'), 'ITC titolo')
         self.assertEqual(self.trans_it('Welcome %(user)s!', user='John'),
                          'Benvenuto John!')
+
+    def test_display_unknown_message(self):
+        self.assertEqual(self.trans('Unknown message'), 'Unknown message')