If the following validator is set to the QLineEdit, isModified always return false.

Here is the validator can be used to reproduce the problem:
class UpperValidator : public QValidator
{
public:
UpperValidator(QObject * parent) : QValidator(parent) {};
~UpperValidator() {};
virtual State validate ( QString & input, int & pos ) const
{
input = input.toUpper();
return Acceptable;
};
};