Tree with leading '0' modes in 1.7.0.3

Mike (CC'd) found a bad Git tree today, where the modes for subtrees where formatted using a leading '0':

  $ od -c tree
  0000000   1   0   0   6   4   4       R   E   A   D   M   E  \0 244  \r
  0000020 233 214 350 375   0 263 374 227 264 343   $ 031 027   ` 373 301
  0000040   !   h   0   4   0   0   0   0       m   o   d   u   l   e   s
  0000060  \0 262   z   K 240   4 377   \ 245   C   c   " 231 377  \n   t
  0000100   ,  \n   O   R   E   0   4   0   0   0   0       s   t   e   w
  0000120   a   r   d   b   o   t  \0 037  \b   5 262 345 234 034 303   C
  0000140 373 335 207 300   u 341 277  \f   ] 320 207
  0000153

The '0' on the 3rd line after '! h' is wrong. It shouldn't be here. Likewise the '0' on the 5th line after "O R E" is also wrong. At least its consistently broken. But its still broken by fsck standards:

 $ git fsck --full a39aa6d
 warning in tree a39aa6d4a6dcfd6c14d8f818bbdf1dfcb3e11771: contains zero-padded file modes

Mike claims this tree was created with git-core 1.7.0.3. This thread actually started over on Gerrit Code Review's mailing list [1], because JGit refuses to allow this malformed tree mode to pass its fsck implementation.

Any ideas?  Why is Git 1.7.0.3 jamming a leading '0' on a file mode?

[1] https://groups.google.com/group/repo-discuss/browse_thread/thread/6ff8d7ffba5a9775