Author and Wharton Professor Jeremy Siegel says that, if the Federal Reserve does start increasing interest rates in September, it could be a blessing for the stock market.

Siegel tells CNBC that many investors are waiting to buy stocks until after the rate hikes begin because they fear the rate increases will hurt the market. But he thinks the anticipation of the rate hikes is worse than the reality will be. He says that once investors see a minor increase isn’t the end of the world, they will start snatching up stocks, making the 4th quarter the best of the year for equities.

Siegel also says that he expects interest rates to stay low for “many years, if not a decade or longer.” Given that, he says that the broader market will be able to support higher P/E ratios. He expects to use P/Es to vacillate between 15 and 22 while interest rates are low, levels that he does not think are high.