diff --git a/src/calibre/ebooks/conversion/plugins/mobi_input.py b/src/calibre/ebooks/conversion/plugins/mobi_input.py
index 3817a7bda9..df65715450 100644
--- a/src/calibre/ebooks/conversion/plugins/mobi_input.py
+++ b/src/calibre/ebooks/conversion/plugins/mobi_input.py
@@ -7,22 +7,6 @@ import os
 
 from calibre.customize.conversion import InputFormatPlugin
 
-def run_mobi_unpack(stream, options, log, accelerators):
-    from mobiunpack.mobi_unpack import Mobi8Reader
-    from calibre.customize.ui import plugin_for_input_format
-    from calibre.ptempfile import PersistentTemporaryDirectory
-
-    wdir = PersistentTemporaryDirectory('_unpack_space')
-    m8r = Mobi8Reader(stream, wdir)
-    if m8r.isK8():
-        epub_path = m8r.processMobi8()
-        epub_input = plugin_for_input_format('epub')
-        for opt in epub_input.options:
-            setattr(options, opt.option.name, opt.recommended_value)
-        options.input_encoding = m8r.getCodec()
-        return epub_input.convert(open(epub_path,'rb'), options,
-                'epub', log, accelerators)
-
 class MOBIInput(InputFormatPlugin):
 
     name        = 'MOBI Input'
@@ -34,14 +18,6 @@ class MOBIInput(InputFormatPlugin):
                 accelerators):
         self.is_kf8 = False
 
-        if os.environ.get('USE_MOBIUNPACK', None) is not None:
-            pos = stream.tell()
-            try:
-                return run_mobi_unpack(stream, options, log, accelerators)
-            except Exception:
-                log.exception('mobi_unpack code not working')
-            stream.seek(pos)
-
         from calibre.ebooks.mobi.reader.mobi6 import MobiReader
         from lxml import html
         parse_cache = {}
diff --git a/src/calibre/ebooks/conversion/plugins/mobi_output.py b/src/calibre/ebooks/conversion/plugins/mobi_output.py
index b73d6341f9..e759df5b78 100644
--- a/src/calibre/ebooks/conversion/plugins/mobi_output.py
+++ b/src/calibre/ebooks/conversion/plugins/mobi_output.py
@@ -174,6 +174,13 @@ class MOBIOutput(OutputFormatPlugin):
                 add_fonts=create_kf8)
         self.check_for_periodical()
 
+        if create_kf8:
+            # Split on pagebreaks so that the resulting KF8 works better with
+            # calibre's viewer, which does not support CSS page breaks
+            from calibre.ebooks.oeb.transforms.split import Split
+            Split()(self.oeb, self.opts)
+
+
         kf8 = self.create_kf8(resources, for_joint=mobi_type=='both'
                 ) if create_kf8 else None
         if mobi_type == 'new':