"KeyError: 'sig'" attempting to download youtube video

[netllama]

$ youtube-dl  "https://www.youtube.com/watch?v=unNa-9qGkfI"
[youtube] Setting language
[youtube] unNa-9qGkfI: Downloading video webpage
[youtube] unNa-9qGkfI: Downloading video info webpage
[youtube] unNa-9qGkfI: Extracting video information
Traceback (most recent call last):
  File "/usr/lib64/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib64/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/bin/youtube-dl/__main__.py", line 18, in <module>
  File "/usr/bin/youtube-dl/youtube_dl/__init__.py", line 606, in main

  File "/usr/bin/youtube-dl/youtube_dl/__init__.py", line 590, in _real_main

  File "/usr/bin/youtube-dl/youtube_dl/FileDownloader.py", line 727, in download
  File "/usr/bin/youtube-dl/youtube_dl/FileDownloader.py", line 465, in extract_info
  File "/usr/bin/youtube-dl/youtube_dl/InfoExtractors.py", line 99, in extract
  File "/usr/bin/youtube-dl/youtube_dl/InfoExtractors.py", line 735, in _real_extract
KeyError: 'sig'

$ youtube-dl --version
2013.06.21

[awojnowski]

Duplicate of #897