Economic activity in the U.S. manufacturing sector gained strength in December. It was the first increase in four months.

The Institute for Supply Management said its Purchasing Managers Index (PMI) stood at 54.7 in December, up from the 49.2 reading in November.

A reading above 50 indicates manufacturing activity is growing, while a figure below 50 suggests contraction.

“The manufacturing sector rebounded in December,” ISM chair Norbert Ore said in a news release.

A strong showing in New Orders drove the PMI upward, while the Production Index strengthened and helped push the PMI up by 5.5 percentage points.