diff --git a/src/calibre/devices/usbms/device.py b/src/calibre/devices/usbms/device.py
index ef2800b1cc..c9a9c2a942 100644
--- a/src/calibre/devices/usbms/device.py
+++ b/src/calibre/devices/usbms/device.py
@@ -6,7 +6,7 @@ intended to be subclassed with the relevant parts implemented for a particular
 device. This class handles devive detection.
 '''
 
-import os, subprocess, time
+import os, re, subprocess, time
 
 from calibre.devices.interface import Device as _Device
 from calibre.devices.errors import DeviceError
@@ -188,8 +188,8 @@ class Device(_Device):
         if not drives:
             raise DeviceError(_('Unable to detect the %s disk drive. Try rebooting.') % self.__class__.__name__)
             
-        self._main_prefix = drives['main'] if 'main' in names.keys() else None
-        self._card_prefix = drives['card'] if 'card' in names.keys() else None
+        self._main_prefix = drives['main'] if 'main' in drives.keys() else None
+        self._card_prefix = drives['card'] if 'card' in drives.keys() else None
 
     @classmethod
     def get_osx_mountpoints(self, raw=None):