auth-constraint with role name ** does not work as specified

The following security constraint does not work as expected:

    <security-constraint>
        <display-name>secure resource</display-name>
        <web-resource-collection>
            <web-resource-name>welcome page</web-resource-name>
            <url-pattern>/*</url-pattern>
        </web-resource-collection>
        <auth-constraint>
            <role-name>**</role-name>
        </auth-constraint>
    </security-constraint>

According to Servlet Specification 3.1, section 13.8, any authenticated user should be able to access the secured resources, but all I get is a Forbidden error page.

Stepping through the code, I can see that ServletSecurityRoleHandler is processing a SingleConstraintMatch with emptyRoleSemantic == PERMIT and requiredRoles == [**].

More likely, this should be emptyRoleSemantic == AUTHENTICATE and requiredRoles == [].