Increase in discount rate increases interest cost?

Part of Solution to question 15 Mock says: An increase in the discount rate will reduce the present value of the future pension benefits and hence decrease service cost. It will increase the interest expense component of pension expense, but typically the decrease in the present value is greater than the increase in the interest component; the exception is when the pension obligation is of short obligation. Ok so they’re saying an INCREASE in the discount rate will REDUCE the interest expense. Schweser says this only happens in mature plans. No mention is made about this being a mature plan. Thoughts?

Someone posted this EXACT question today about short duration vs. mature plans. Search for it.