Starting single player game fails on win32

trunk 5244, mingw32:
If you do start a single player map, widelands fails to load the winning condition lua script:

Unerwarteter Fehler im Spielverlauf
Could not find file: could not find file or directory: scripting/win_conditions/win_conditions\00_endless_game.lua

But stdout shows the script loaded and registered:

[snip]
Registering script: (aux,table)
Registering script: (win_conditions,win_conditions\00_endless_game)
Registering script: (win_conditions,win_conditions\01_defeat_all)
Registering script: (win_conditions,win_conditions\02_collectors)
Registering script: (win_conditions,win_conditions\03_tribes_together)
textdomain win_conditions @ H:\wl_build\locale
textdomain win_conditions @ H:\wl_build\locale
[...]

Looks like a /,\ file path problem to me...