Equity investors hoping to keep riding the current upswell in the markets could be in for a shock, according to Peter Oppenheimer, chief global equities strategist at Goldman Sachs.
With the S&P 500 up nearly 7 percent year-to-date and hitting all-time highs, the Goldman strategist believed that investors might be getting complacent.
"We feel that it's not a goldilocks scenario," he told CNBC Wednesday.
"Markets will be stuck in a relatively flat return environment, with valuations peaking out but with quite a volatile range as you get sentiment swinging between fears of deflation on the one hand and optimism about reflation on the other."
The "Goldilocks" scenario is used by the investment community to describe an environment where asset prices, or the economy in general, are not too hot or cold. However, the description Oppenheimer has used all year is "fat and flat" and stuck by that analogy on Wednesday.
"I think that the goldilocks that's been building up over the last two months or so is really a belief that you're not going to get (Federal Reserve) rate rises really forever on the one hand. But on the other hand you've had this narrative that fiscal policy is suddenly going to be expanded rapidly everywhere and that's going to boost growth. And I think that combination I think is too optimistic and the rally that we've seen we think is reaching it's very mature stages," he added.