diff --git a/src/calibre/ebooks/mobi/debug/headers.py b/src/calibre/ebooks/mobi/debug/headers.py
index 5b80a46f1b..2b5d6920a5 100644
--- a/src/calibre/ebooks/mobi/debug/headers.py
+++ b/src/calibre/ebooks/mobi/debug/headers.py
@@ -144,9 +144,9 @@ class EXTHRecord(object):
                 118 : 'retailprice',
                 119 : 'retailpricecurrency',
                 121 : 'KF8 header section index',
-                125 : 'KF8 resources (images/fonts) count',
-                129 : 'KF8 cover URI',
-                131 : 'KF8 unknown count',
+                125 : 'KF8 unknown count',
+                129 : 'KF8 thumbnail URI',
+                131 : 'KF8 resources (images/fonts) count',
                 201 : 'coveroffset',
                 202 : 'thumboffset',
                 203 : 'hasfakecover',
diff --git a/src/calibre/ebooks/mobi/writer8/exth.py b/src/calibre/ebooks/mobi/writer8/exth.py
index 508b77ce5b..603767b3d7 100644
--- a/src/calibre/ebooks/mobi/writer8/exth.py
+++ b/src/calibre/ebooks/mobi/writer8/exth.py
@@ -29,8 +29,9 @@ EXTH_CODES = {
     'versionnumber': 114,
     'startreading': 116,
     'kf8_header_index': 121,
-    'num_of_resources': 125,
-    'kf8_unknown_count': 131,
+    'kf8_unknown_count': 125,
+    'kf8_thumbnail_uri': 129,
+    'num_of_resources': 131,
     'coveroffset': 201,
     'thumboffset': 202,
     'hasfakecover': 203,
@@ -159,7 +160,10 @@ def build_exth(metadata, prefer_author_sort=False, is_periodical=False,
     if thumbnail_offset is not None:
         exth.write(pack(b'>III', EXTH_CODES['thumboffset'], 12,
             thumbnail_offset))
-        nrecs += 1
+        cover_uri_str = bytes('kindle:embed:%04X' %(thumbnail_offset))
+        exth.write(pack(b'>II', EXTH_CODES['kf8_cover_uri'], len(cover_uri_str) + 8))
+        exth.write(cover_uri_str)
+        nrecs += 2
 
     if start_offset is not None:
         try: