Shares of Walmart ( WMT -4.53%) fell 4.9% Thursday. The drop came as the S&P 500 lost 0.5% and the Nasdaq Composite lost 0.4% as investors await Federal Reserve Chair Jerome Powell's speech tomorrow.

The $100 level acted as support earlier in August. But since February, $100 has been a pretty strong resistance level. Now that WMT stock is below it once more, it is a worrying sign. Shares of Walmart rarely go on sale unless the market perceives a macro shock.

Stocks opened lower Thursday, under pressure after a larger-than-expected rise in first-time unemployment claims and disappointing results from Walmart that saw the retail behemoth and Dow component miss Wall Street profit expectations.