diff --git a/src/calibre/ebooks/mobi/debug/mobi6.py b/src/calibre/ebooks/mobi/debug/mobi6.py
index 640f58c661..fb5674653c 100644
--- a/src/calibre/ebooks/mobi/debug/mobi6.py
+++ b/src/calibre/ebooks/mobi/debug/mobi6.py
@@ -393,7 +393,7 @@ class IndexRecord(object): # {{{
 
             parse_index_record(table, record.raw,
                     index_header.tagx_control_byte_count, tags,
-                    index_header.index_encoding, strict=True)
+                    index_header.index_encoding, {}, strict=True)
 
         self.indices = []
 
diff --git a/src/calibre/ebooks/mobi/debug/mobi8.py b/src/calibre/ebooks/mobi/debug/mobi8.py
index b869b8b69b..458b2d4893 100644
--- a/src/calibre/ebooks/mobi/debug/mobi8.py
+++ b/src/calibre/ebooks/mobi/debug/mobi8.py
@@ -82,7 +82,7 @@ class MOBIFile(object):
 
         if self.header.fdst_idx != NULL_INDEX:
             idx = self.header.fdst_idx
-            self.fdst = FDST(self.kf8_records[idx].raw)
+            self.fdst = FDST(self.mf.records[idx].raw)
             if self.fdst.num_sections != self.header.fdst_count:
                 raise ValueError('KF8 Header contains invalid FDST count')