diff --git a/src/calibre/ebooks/mobi/writer8/exth.py b/src/calibre/ebooks/mobi/writer8/exth.py
index 81a0c7669d..dc3f850dba 100644
--- a/src/calibre/ebooks/mobi/writer8/exth.py
+++ b/src/calibre/ebooks/mobi/writer8/exth.py
@@ -11,6 +11,7 @@ import re
 from struct import pack
 from io import BytesIO
 
+from calibre.constants import iswindows, isosx
 from calibre.ebooks.mobi.utils import (utf8_text, to_base)
 from calibre.utils.localization import lang_as_iso639_1
 from calibre.ebooks.metadata import authors_to_sort_string
@@ -149,7 +150,8 @@ def build_exth(metadata, prefer_author_sort=False, is_periodical=False,
         nrecs += 1
 
     if be_kindlegen2:
-        vals = {204:202, 205:2, 206:9, 207:0}
+        mv = 200 if iswindows else 202 if isosx else 201
+        vals = {204:mv, 205:2, 206:9, 207:0}
     elif is_periodical:
         # Pretend to be amazon's super secret periodical generator
         vals = {204:201, 205:2, 206:0, 207:101}