diff --git a/src/calibre/ebooks/mobi/reader.py b/src/calibre/ebooks/mobi/reader.py
index 2c80cc1c8c..3ca1fd6c18 100644
--- a/src/calibre/ebooks/mobi/reader.py
+++ b/src/calibre/ebooks/mobi/reader.py
@@ -370,6 +370,11 @@ class MobiReader(object):
             opf.cover = 'images/%05d.jpg'%(self.book_header.exth.cover_offset+1)
         elif mi.cover is not None:
             opf.cover = mi.cover
+        else:
+            opf.cover = 'images/%05d.jpg'%1
+            if not os.path.exists(os.path.join(os.path.dirname(htmlfile), 
+                                               *opf.cover.split('/'))):
+                opf.cover = None
         manifest = [(htmlfile, 'text/x-oeb1-document')]
         bp = os.path.dirname(htmlfile)
         for i in getattr(self, 'image_names', []):