diff --git a/obd_io.py b/obd_io.py
index a20a0a5..e30f103 100755
--- a/obd_io.py
+++ b/obd_io.py
@@ -84,11 +84,12 @@ class OBDPort:
          self._notify_window=_notify_window
          wx.PostEvent(self._notify_window, DebugEvent([1,"Opening interface (serial port)"]))                
 
+         self.port = None
          try:
              self.port = serial.Serial(portnum,baud, \
              parity = par, stopbits = sb, bytesize = databits,timeout = to)
              
-         except serial.SerialException:
+         except (serial.SerialException, OSError):
              self.State = 0
              return None