Extraction fails

[fstirlitz]

$ python2 extract.py vol2a.pdf vol2b.pdf
Processing page 1
[...]
Processing page 670
Processing page 671
Processing page 672
Writing to html/Intel® 64 and IA.html
Traceback (most recent call last):
  File "extract.py", line 40, in <module>
    result = main(sys.argv)
  File "extract.py", line 34, in main
    parser.flush()
  File "x86manual.py", line 239, in flush
    self.__output_file(displayable)
  File "x86manual.py", line 354, in __output_file
    file_data = self.__output_page(displayable).encode("UTF-8")
  File "x86manual.py", line 373, in __output_page
    text.append(self.__output_html(element))
  File "x86manual.py", line 385, in __output_html
    result = self.__output_text(element)
  File "x86manual.py", line 539, in __output_text
    elif element.font_name() == "NeoSansIntel" and self.__title_stack[-1] == "operation":
IndexError: list index out of range