Bank of America stock dropped 5.3% in mid-day trading on Monday after CEO Brian Moynihan said the bank expects third-quarter investment banking fees between $1.6 billion and $1.8 billion, representing a decline of at least 10% from the same period last year.

Moynihan made the comments at the Barclays Global Financial Services Conference. He said the expected decline stems from a slowdown in the investment banking market, with the industry overall tracking roughly 10% lower.

The forecast marks a shift from the bank's performance earlier in the year. Second-quarter investment banking fees reached $2.1 billion, exceeding analyst expectations.

Moynihan also said third-quarter sales and trading revenue is expected to remain roughly flat compared to the second quarter.

The bank's equity strategist separately noted that the S&P 500 is statistically overdue for a pullback given the historically weak September-October seasonal period.