Merge Noto Sans 2.0 and Noto Naskh Arabic

[schwantuschke]

Hello,

i want to merge the font Noto Sans 2.0 from google.com/get/noto and the font Noto Naskh Arabic from same website.
Unfortunately i get errors and don't understand:

Traceback (most recent call last):
  File "merge_fonts.py", line 120, in <module>
    main()
 File "merge_fonts.py", line 107, in main
    font = merger.merge(valid_files)
File "/usr/local/lib/python2.7/site-packages/fontTools/merge.py", line 966, in merge
    table = clazz(tag).merge(self, tables)
File "/usr/local/lib/python2.7/site-packages/fontTools/merge.py", line 160, in merge
    return m.mergeObjects(self, self.mergeMap, tables)
File "/usr/local/lib/python2.7/site-packages/fontTools/merge.py", line 1012, in mergeObjects
    value = mergeLogic(getattr(table, key, NotImplemented) for table in tables)
File "/usr/local/lib/python2.7/site-packages/fontTools/merge.py", line 49, in equal
    assert all(item == first for item in t), "Expected all items to be equal: %s" % lst
AssertionError: Expected all items to be equal: [1000, 2048]

If i merge the Noto Sans 1.04 from fonts.google.com and the Noto Naskh Arabic it works well.