diff --git a/src/calibre/ebooks/mobi/writer8/main.py b/src/calibre/ebooks/mobi/writer8/main.py
index c9334b22a3..430d695fd1 100644
--- a/src/calibre/ebooks/mobi/writer8/main.py
+++ b/src/calibre/ebooks/mobi/writer8/main.py
@@ -175,7 +175,7 @@ class KF8Writer(object):
         self.link_map = {}
         count = 0
         hrefs = {item.href for item in self.oeb.spine}
-        for i, item in enumerate(self.oeb.spine):
+        for item in self.oeb.spine:
             root = self.data(item)
 
             for a in XPath('//h:a[@href]')(root):
@@ -184,8 +184,7 @@ class KF8Writer(object):
                 href, _, frag = ref.partition('#')
                 href = urlnormalize(href)
                 if href in hrefs:
-                    placeholder = 'kindle:pos:fid:%04d:off:%s'%(i,
-                            to_href(count))
+                    placeholder = 'kindle:pos:fid:0000:off:%s'%to_href(count)
                     self.link_map[placeholder] = (href, frag)
                     a.set('href', placeholder)
 
@@ -201,9 +200,9 @@ class KF8Writer(object):
                     aid = aidbase + j
                     tag.attrib['aid'] = to_base(aid, base=32)
                     if tag.tag == XHTML('body'):
-                        self.id_map[(item.href, '')] = tag.attrib['aid']
+                        self.id_map[(item.href, '')] = (i, tag.attrib['aid'])
                     if id_ is not None:
-                        self.id_map[(item.href, id_)] = tag.attrib['aid']
+                        self.id_map[(item.href, id_)] = (i, tag.attrib['aid'])
 
                     j += 1
 
diff --git a/src/calibre/ebooks/mobi/writer8/skeleton.py b/src/calibre/ebooks/mobi/writer8/skeleton.py
index 4b39d0cb15..494aa30def 100644
--- a/src/calibre/ebooks/mobi/writer8/skeleton.py
+++ b/src/calibre/ebooks/mobi/writer8/skeleton.py
@@ -341,7 +341,12 @@ class Chunker(object):
         for match in re.finditer(br'<[^>]+? aid=[\'"]([A-Z0-9]+)[\'"]', text):
             aid_map[match.group(1)] = match.start()
         self.aid_offset_map = aid_map
-        placeholder_map = {bytes(k):bytes(to_href(aid_map[v])) for k, v in
+
+        def to_placeholder(x):
+            file_number, aid = x
+            return bytes('%04d:%s'%(file_number, to_href(aid_map[aid])))
+
+        placeholder_map = {bytes(k):to_placeholder(v) for k, v in
                 self.placeholder_map.iteritems()}
 
         # Now update the links
@@ -349,7 +354,7 @@ class Chunker(object):
             raw = match.group()
             pl = match.group(1)
             try:
-                return raw[:-10] + placeholder_map[pl]
+                return raw[:-15] + placeholder_map[pl]
             except KeyError:
                 pass
             return raw