401(k) - 403(b) coverage test

[waid10]

We have a nonprofit parent that sponsors a 403(b) plan and a for-profit subsidiary with a 401(k) plan. I am being told that our 401(k) fails the 410(b) coverage test because the employees in the 403(b) plan cannot participate in the 401(k). I am nearly certain that there is an exception and the employees in the 403(b) don't have to be counted in the 401(k) coverage test. Am I correct? Can someone point me to the law/regs on this?

Thanks.

[Guest Sieve]

Treas. Reg. Section 1.410(b)-6(g)(3).