diff --git a/rencode/_rencode.pyx b/rencode/_rencode.pyx
index 5716c2d..14e1bec 100644
--- a/rencode/_rencode.pyx	2021-08-05 21:15:32.117793791 +0700
+++ b/rencode/_rencode.pyx	2021-08-05 21:15:29.931809176 +0700
@@ -527,6 +527,9 @@
         return decode_fixed_dict(data, pos)
     elif typecode == CHR_DICT:
         return decode_dict(data, pos)
+    else:
+        raise Exception("invalid typecode %i" % typecode)
+
 
 def loads(data, decode_utf8=False):
     """
diff --git a/tests/test_rencode.py b/tests/test_rencode.py
index 0081a1c..63cd3df 100644
--- a/tests/test_rencode.py
+++ b/tests/test_rencode.py
@@ -212,5 +212,14 @@ class TestRencode(unittest.TestCase):
         assert rencode_orig.__version__
         self.assertEqual(rencode.__version__[1:], rencode_orig.__version__[1:], "version number does not match")
 
+    def test_invalidtypecode(self):
+        s = b';\x2f\x7f'
+        try:
+            rencode.loads(s)
+        except Exception:
+            pass
+        else:
+            raise Exception("invalid typecode should raise an Exception")
+
 if __name__ == '__main__':
     unittest.main()