diff --git a/trezorlib/transport_hid.py b/trezorlib/transport_hid.py
index 6ee531c17..aaea6a716 100644
--- a/trezorlib/transport_hid.py
+++ b/trezorlib/transport_hid.py
@@ -87,7 +87,7 @@ class _HidTransport(object):
             raise Exception("Unexpected data length")
 
         if self.hid_version == 2:
-            self.hid.write([0,] + chunk)
+            self.hid.write(b'\0' + chunk)
         else:
             self.hid.write(chunk)