SSIS, TFS and Error Message "cannot convert between unicode and non-unicode string data types."

Hi

I created a package that transfer data from a delimited text files into database table in oracle 11g. The data type while transferring was String[DT_STR], the package worked well so far.

However, when I uploaded the package to TFS (Team Foundation Server), and a team member checked out the package in his machine, he got the error: "cannot convert between Unicode and non-Unicode string data types." for all columns. The fix on my coworker machine is to convert to Unicode "Unicode string [DT_WSTR]".

After that, when I get the package back from my coworker, I have to convert back to String[DT_STR] in order to work in my machine.

How can I make my package accessible to my coworker and me without modifications?

Thanks.