diff --git a/src/calibre/ebooks/metadata/mobi.py b/src/calibre/ebooks/metadata/mobi.py
index 687791e5ac..07c68b06d9 100644
--- a/src/calibre/ebooks/metadata/mobi.py
+++ b/src/calibre/ebooks/metadata/mobi.py
@@ -402,6 +402,7 @@ class MetadataUpdater(object):
 
         if asin is not None:
             update_exth_record((113, asin.encode(self.codec)))
+            update_exth_record((501, b'EBOK'))
             update_exth_record((504, asin.encode(self.codec)))
 
         # Add a 112 record with actual UUID