Regex and Unicode

Hi, I'm trying to use Unicode with Regex in an MFC app. The preprocessor variable UNICODE is defined. But I obtain an error on the line : regex_search(sText, oResults, pRegExp); error C2665: none of the 4 overloads can convert parameter 1 from type 'class CString' sText is a CString which has a "const wchar_t*" operator. The problem is why doesn't the regex_search prototype require a "const wchar_t*" when UNICODE is defined ? Thanks. Fred (I read the documentation, but maybe I missed something...)