option to normalize case for zip imports?

I've run into a problem when I try to import two zip archives containing files whose names differ only in case. In particular,

C:\mines-perfect-srcdists>unzip -l mines100_src.zip
Archive: mines100_src.zip
  Length Date Time Name
 -------- ---- ---- ----
     5256 08/07/00 09:06 Mineperf.bpr
    37142 08/07/00 08:15 board.cpp
    47729 08/07/00 08:15 eqs.cpp
     2113 08/07/00 08:15 Mineperf.cpp
     7325 08/07/00 08:15 PARAM.CPP
     1357 08/07/00 08:15 UNITINFO.CPP
    35826 08/07/00 13:00 UnitMain.cpp
    16123 08/07/00 08:16 UNITMINE.CPP
     1375 08/07/00 08:16 UNITNREC.CPP
     1355 08/07/00 08:16 UNITSIZE.CPP
     2271 08/07/00 08:16 UNITSREC.CPP
     1786 08/07/00 13:24 UnitInfo.dfm
    15263 08/07/00 09:02 UnitMain.dfm
    14528 04/06/99 19:25 UNITMINE.DFM
     1837 06/06/00 09:56 UNITNREC.DFM
     1847 04/14/99 21:37 UNITSIZE.DFM
     1778 06/06/00 10:03 UNITSREC.DFM
     6693 08/07/00 08:15 board.h
     3714 08/07/00 08:15 cell.h
    11624 08/07/00 08:15 eqs.h
     3677 08/07/00 08:15 PARAM.H
     1832 08/07/00 08:55 UnitInfo.h
     8303 08/07/00 08:16 UnitMain.h
     4701 08/07/00 08:16 UNITMINE.H
     1820 08/07/00 08:16 UNITNREC.H
     1820 08/07/00 08:16 UNITSIZE.H
     2149 08/07/00 08:13 UNITSREC.H
      191 08/07/00 13:55 changelog.txt
    18351 08/07/00 08:54 copying.txt
      363 08/07/00 13:45 readme.txt
 -------- -------
   260149 30 files

C:\mines-perfect-srcdists>unzip -l mines101_src.zip
Archive: mines101_src.zip
  Length Date Time Name
 -------- ---- ---- ----
     5256 10/07/00 09:17 Mineperf.bpr
     1786 10/07/00 13:22 UnitInfo.dfm
     1781 10/07/00 09:53 UnitSRec.dfm
     2271 10/07/00 08:21 UnitSRec.cpp
     1820 10/07/00 08:21 Unitsize.h
     1355 10/07/00 08:21 Unitsize.cpp
     1820 10/07/00 08:21 Unitnrec.h
     1375 10/07/00 08:21 Unitnrec.cpp
     4701 10/07/00 08:21 Unitmine.h
    16123 10/07/00 08:21 Unitmine.cpp
     8303 10/07/00 08:21 UnitMain.h
    35870 10/07/00 09:15 UnitMain.cpp
     1832 10/07/00 08:55 UnitInfo.h
     1357 10/07/00 08:20 UnitInfo.cpp
     3677 10/07/00 08:20 Param.h
     7325 10/07/00 08:20 Param.cpp
     2119 10/07/00 08:20 Mineperf.cpp
    12128 10/07/00 08:20 eqs.h
    48440 10/07/00 08:20 eqs.cpp
     3511 10/07/00 08:20 cell.h
     6694 10/07/00 08:20 board.h
    38308 10/07/00 08:20 board.cpp
     2149 10/07/00 08:20 UnitSRec.h
    15263 10/07/00 09:14 UnitMain.dfm
    24251 08/02/00 17:13 Mineperf.rtf
     1837 06/06/00 09:56 Unitnrec.dfm
     1847 04/14/99 21:37 Unitsize.dfm
    14528 04/06/99 19:25 Unitmine.dfm
    18351 10/07/00 08:54 copying.txt
      363 10/07/00 13:45 readme.txt
      650 10/07/00 13:54 changelog.txt
 -------- -------
   287091 31 files

Here on Windows, trying to import the 2nd of these after having committed the first one gives me a bzrlib.errors.MalformedTransform. Presumably I'd just get an almost useless history if I did this on *nix, so it's not really a windows-only problem...

(Incidentally, it seems to leave the tree locked after this!)