Apple Inc.’s (NASDAQ:AAPL) record-breaking fiscal third quarter is being overshadowed by looming fourth-quarter supply shortages.

The surprising culprit?

The tech giant underestimated consumer demand for its own products, contributing to a weaker-than-expected September-quarter outlook and a sharp drop in after-hours trading.

'A Demand Forecast Issue' Despite posting its strongest June quarter ever, Apple expects its September-quarter revenue growth to decelerate to 9% to 11%.

The company projects fourth-quarter sales between $111.69 billion and $113.74 billion, trailing Wall Street’s $114.84 billion estimate and sending AAPL shares down over 6% in overnight trading.