RequiredFieldValidator in a custom WizardStep of CreateUserWizard does not work

Hello,
I am having a problem with a RequiredFieldValidator I put inside a custom WizardStep of CreateUserWizard. The validator simply does not work. The custom WizardStep is before CreateUserWizardStep and the user can go from the custom WizardStep to the CreateUserWizardStep using the Next button, which was automatically added, even if the field to be validated is left empty. Does anyone have an idea, why? Here is the code of the field on the custom WizardStep to be validated along with the RequiredFieldValidator:


<asp:TextBox Text=""< ...