We just upgraded from TC 15.00 x64 to TC 18.00.18 x64. We have some lua scripts that execute .bat files via io.popen(). The argument to popen() is a table, with the first entry being a quoted string of the full path to the .bat file with Unix style slashes. Subsequent arguments are parameters to the batch file. Something like this: args = '"D:/dev/bin/SyncP4Changelist.bat"' args = 'option1' They worked fine under TC 15.00 but don't from a 18.00 TC Prompt. We see this error message when the popen() call is made: TCC: Unknown command "D:" If I enable UNIX/Linux-style paths I get this error: TCC: Unknown command "D:/dev/bin/SyncP4Changelist.bat option1" If I remove the double quotes from args it works. I'd prefer not to have to do that as it may break compatibility with other shells and there are a lot of lua scripts I'd have to change. Thanks.