diff --git a/pyxid/pyxid_impl.py b/pyxid/pyxid_impl.py
index 70d8de9..2cd057f 100644
--- a/pyxid/pyxid_impl.py
+++ b/pyxid/pyxid_impl.py
@@ -404,7 +404,7 @@ def init_device(self):
                     rb_834_keymap)
             else:
                 raise XidError('Unknown RB Device')
-        elif product_id == 'S':
+        elif product_id == b'S':
             fw_major = int(self._send_command('_d4', 1))
             fw_minor = int(self._send_command('_d5', 1))