diff --git a/test_iconv.py b/test_iconv.py
index c6b9de1..87f6224 100644
--- a/test_iconv.py
+++ b/test_iconv.py
@@ -12,3 +12,10 @@ def test_with_length(self):
         s = iconv.open("utf-16le", "utf-8")
         r = s.iconv(b"Hallo", 11)
         self.assertEqual(r, "Hallo".encode("utf-16le"))
+
+    def test_incorrect_input_type(self):
+        s = iconv.open("latin1", "utf-8")
+        with self.assertRaisesRegex(
+            TypeError, "iconv expects byte object as first argument"
+        ):
+            r = s.iconv("Hallo")