porting std::wstring from visual studio to mingw gcc

I am in the process of porting some code from Visual studio to mingw gcc. I came across this statement

if ( mnode.GetTag() == _T( "val" ) )    
        return  true;

this is the definition of GetTag() method

const std::wstring &GetTag() const;

I am getting the error

error: no matching function for call to 'std::basic_string<wchar_t>::basic_string(const char [6])'|

Now after reading this I am still not sure how to resolve this issue. Any suggestions on why this error is being shown up ? is it because of wstring ?