allocating shareholder capital to pension plan question conclusion, question, capital, because, change

Iginla2010

Hello, schweser book 2 page 59, it says
firm equity beta / firm asset beta =(1+D/E)

and the conclusion is debt-equity ratio increases, its equity beta increases... it sounds like firm asset beta desn't change...

I got confused because I think it makes a lot more sense to say debt/equity increases, then the firm asset beta decreases!

please help! thanks!