diff --git a/src/calibre/devices/usbms/books.py b/src/calibre/devices/usbms/books.py
index 4f530f38cf..507ee5ff91 100644
--- a/src/calibre/devices/usbms/books.py
+++ b/src/calibre/devices/usbms/books.py
@@ -24,7 +24,10 @@ def none_cmp(xx, yy):
     y = yy[1]
     if x is None and y is None:
         # No sort_key needed here, because defaults are ascii
-        return cmp(xx[2], yy[2])
+        try:
+            return cmp(xx[2], yy[2])
+        except TypeError:
+            return 0
     if x is None:
         return 1
     if y is None: