Replacing of tmp path not working for private file handling

Hi,
don't know if anyone has come across this problem or if I'm doing something wrong. Am using FilePath in combination with FileField Insert and file system is set to private. On insert FileFieldInsert inserts the tmp path to the file, on save FilePath should then replace the tmp path with the final path. Didn't work for me as in 497 the reg expression is being set up with file_directory_path() which returns "sites/default/files" for me, but the tmp path starts with "system/files". Looked for the proper function but couldn't find it right away, so I deleted file_directory_path() in the first part of regex, regex_enc and replace. Shouldn't be done that way, but works for me know. Or how is it supposted to work in my case?