diff --git a/src/calibre/ebooks/mobi/reader/headers.py b/src/calibre/ebooks/mobi/reader/headers.py
index 90fdb0e8df..51da05ea83 100644
--- a/src/calibre/ebooks/mobi/reader/headers.py
+++ b/src/calibre/ebooks/mobi/reader/headers.py
@@ -28,6 +28,7 @@ class EXTHHeader(object): # {{{
         self.start_offset = None
         left = self.num_items
         self.kf8_header = None
+        self.uuid = self.cdetype = None
 
         while left > 0:
             left -= 1