diff --git a/src/calibre/ebooks/mobi/debug/headers.py b/src/calibre/ebooks/mobi/debug/headers.py
index b5d6cf727f..b38af77774 100644
--- a/src/calibre/ebooks/mobi/debug/headers.py
+++ b/src/calibre/ebooks/mobi/debug/headers.py
@@ -415,8 +415,8 @@ class MOBIHeader(object): # {{{
         if self.has_extra_data_flags:
             a('Unknown4: %r'%self.unknown4)
             if hasattr(self, 'first_text_record'):
-                a('First text record: %d'%self.first_text_record)
-                a('Last text record: %d'%self.last_text_record)
+                a('First content record: %d'%self.first_text_record)
+                a('Last content record: %d'%self.last_text_record)
             else:
                 r('FDST Index', 'fdst_idx')
             a('FDST Count: %d'% self.fdst_count)
diff --git a/src/calibre/ebooks/mobi/writer2/main.py b/src/calibre/ebooks/mobi/writer2/main.py
index 9afd39a211..a1b5c06e33 100644
--- a/src/calibre/ebooks/mobi/writer2/main.py
+++ b/src/calibre/ebooks/mobi/writer2/main.py
@@ -382,6 +382,7 @@ class MobiWriter(object):
             first_image_record  = len(self.records)
             self.resources.serialize(self.records, used_images)
         resource_record_count = len(self.records) - old
+        last_content_record = len(self.records) - 1
 
         # FCIS/FLIS (Seems to serve no purpose)
         flis_number = len(self.records)
@@ -406,7 +407,7 @@ class MobiWriter(object):
         # header
         header_fields['first_resource_record'] = first_image_record
         header_fields['exth_flags'] = 0b100001010000 # Kinglegen uses this
-        header_fields['fdst_record'] = NULL_INDEX
+        header_fields['fdst_record'] = pack(b'>HH', 1, last_content_record)
         header_fields['fdst_count'] = 1 # Why not 0? Kindlegen uses 1
         header_fields['flis_record'] = flis_number
         header_fields['fcis_record'] = fcis_number