diff --git a/src/calibre/ebooks/mobi/writer2/serializer.py b/src/calibre/ebooks/mobi/writer2/serializer.py
index 9bbaa436a7..247adbf7c7 100644
--- a/src/calibre/ebooks/mobi/writer2/serializer.py
+++ b/src/calibre/ebooks/mobi/writer2/serializer.py
@@ -85,7 +85,8 @@ class Serializer(object):
                 spine_item(item).is_section_start = True
                 for i, article in enumerate(articles):
                     si = spine_item(article)
-                    si.is_article_start = True
+                    if si is not None:
+                        si.is_article_start = True
 
         items = list(self.oeb.spine)
         in_sec = in_art = False
@@ -116,7 +117,7 @@ class Serializer(object):
         buf.write(b'</html>')
         self.end_offset = buf.tell()
         self.fixup_links()
-        if self.start_offset is None:
+        if self.start_offset is None and not self.is_periodical:
             # If we don't set a start offset, the stupid Kindle will
             # open the book at the location of the first IndexEntry, which
             # could be anywhere. So ensure the book is always opened at the