diff --git a/src/calibre/devices/kobo/books.py b/src/calibre/devices/kobo/books.py
index 496162d668..f19f4fbc07 100644
--- a/src/calibre/devices/kobo/books.py
+++ b/src/calibre/devices/kobo/books.py
@@ -41,6 +41,10 @@ class Book(MetaInformation):
             self.authors = ['']
         else:
             self.authors = [authors]
+
+        if not title:
+            self.title = _('Unknown')
+
         self.mime = mime
 
         self.size = size # will be set later if None