Contribution limit on owner-employees

A trust forming part of a pension or profit-sharing plan which provides contributions or benefits for employees some or all of whom are owner-employees shall constitute a qualified trust under this section only if, in addition to meeting the requirements of subsection (a), the plan provides that contributions on behalf of any owner-employee may be made only with respect to the earned income of such owner-employee which is derived from the trade or business with respect to which such plan is established.