SqlMembershipProvider: requiresQuestionAndAnswer set to false in web.config but RequiresQuestionAndAnswer is true at runtime

In an ASP.net web application I have defined the following Membership provider in the web.config:

<membership><providers><add connectionStringName="MyServer" name="MyServer" type="System.Web.Security.SqlMembershipProvider"
      enablePasswordReset="true"
      requiresQuestionAndAnswer="false"
      enablePasswordRetrieval="false" /></providers></membership>

When I run the application in the debugger, the property Membership.Provider.RequiresQuestionAndAnswer istrue .

Why? And how can I fix this?