diff --git a/converter.py b/converter.py
index b844efb03b247d677cc91b4859e320da65db1da9..0387c4585c1959f2bc951cec290e29dcc8b6de6c 100644
--- a/converter.py
+++ b/converter.py
@@ -139,6 +139,10 @@ class TestConverter(unittest.TestCase):
         res = self.c.convert(2025)
         self.assertEqual(res, "MMXXV")
 
+    def test_convertSign(self):
+        res = self.c.convert('!')
+        self.assertEqual(res, "Bitte ganze Zahlen eingeben")
+
 
 
 if __name__ == "__main__":