diff --git a/src/calibre/devices/kobo/books.py b/src/calibre/devices/kobo/books.py
index bcf6353e83..fc18a61fc8 100644
--- a/src/calibre/devices/kobo/books.py
+++ b/src/calibre/devices/kobo/books.py
@@ -199,6 +199,11 @@ class KTCollectionsBookList(CollectionsBookList):
                                 ('series' in collection_attributes and
                                  book.get('series', None) == category):
                             is_series = True
+
+                    # The category should not be None, but, it has happened.
+                    if not category:
+                        continue
+
                     cat_name = category.strip(' ,')
 
                     if cat_name not in collections:
diff --git a/src/calibre/devices/kobo/driver.py b/src/calibre/devices/kobo/driver.py
index 0aa946c848..2932c657b0 100644
--- a/src/calibre/devices/kobo/driver.py
+++ b/src/calibre/devices/kobo/driver.py
@@ -1537,7 +1537,11 @@ class KOBOTOUCH(KOBO):
                 return bookshelves
 
             cursor = connection.cursor()
-            query = "select ShelfName from ShelfContent where ContentId = ? and _IsDeleted = 'false'"
+            query = "select ShelfName "         \
+                    "from ShelfContent "        \
+                    "where ContentId = ? "      \
+                    "and _IsDeleted = 'false' " \
+                    "and ShelfName is not null"         # This should never be nulll, but it is protection against an error cause by a sync to the Kobo server
             values = (ContentID, )
             cursor.execute(query, values)
             for i, row in enumerate(cursor):