FX's "The Strain" enjoys a 20% uptick in the adults 18-49 rating. It was the top-rated episode since the premiere.

If satisfaction was the reaction to last week’s stability in the adults 18-49 demographic, then full-on celebration is in order this week.

Sunday’s episode of FX drama “The Strain,” which was the show’s fourth installment, drew an improved 1.2 adults 18-49 rating.

Up 20% from last week’s mark, the rating ties that of the July 13 premiere as a series high.

Despite the bump in adults 18-49, total viewership actually declined this week. Sunday’s episode drew 2.27 million viewers, which was down slightly from the 2.30 million averaged by last week’s episode and the 2.99 million garnered by the premiere.

The second episode, which aired on July 20, drew a weaker viewership count of 2.12 million.

Excitement over the uptick in the ad-friendly adults 18-49 demographic will, nonetheless, more than compensate for any disappointment associated with the decline in viewership.