A couple of indicators signal the NSE Nifty has a key support at 8,400.

The 23.6 pct Fibonacci retracement of the rally from Oct. 17 low of 7723.85 to a record high of 8,626.95 on Dec. 4 rests around 8,414.

Meanwhile, put options at 8,400 reach 5.74 million outstanding positions as of Monday’s close – NSE data.

That level has the highest outstanding positions among index puts.

The NSE has fallen nearly 2 percent so far in December.

Index trading flat at 8,439.65