diff --git a/tests/test_turmit.py b/tests/test_turmit.py
index 096c323..5c42c65 100644
--- a/tests/test_turmit.py
+++ b/tests/test_turmit.py
@@ -213,7 +213,7 @@ class TurmitTestCase(unittest.TestCase):
 
     def test_dup(self):
         ''' Test turmit dup() method '''
-        self._rpn('dup')
+        self._rpn('dup', 1)
 
         t = Turmit()
         t._push(42)