diff --git a/cmd.py b/cmd.py
index 311bcf5778..bed3a5be0b 100755
--- a/cmd.py
+++ b/cmd.py
@@ -114,6 +114,8 @@ class Commands(object):
         return self.client.load_device(seed, args.pin) 
 
     def firmware_update(self, args):
+        if not args.file:
+            raise Exception("Must provide firmware filename")
         fp = open(args.file, 'r')
         if fp.read(4) != 'TRZR':
             raise Exception("Trezor firmware header expected")
diff --git a/trezorlib/transport_hid.py b/trezorlib/transport_hid.py
index b6ee9f253e..98af595201 100644
--- a/trezorlib/transport_hid.py
+++ b/trezorlib/transport_hid.py
@@ -40,7 +40,8 @@ class HidTransport(Transport):
     def _open(self):
         self.buffer = ''
         path = self.device.split(':')
-        self.hid = hid.device(int(path[0], 16), int(path[1], 16))#, path[2])
+        self.hid = hid.device()
+        self.hid.open(int(path[0], 16), int(path[1], 16))
         self.hid.set_nonblocking(True)
         self.hid.send_feature_report([0x41, 0x01]) # enable UART
         self.hid.send_feature_report([0x43, 0x03]) # purge TX/RX FIFOs