Twitter ad engineers are the latest to be laid off, an odd choice given Elon Musk’s determination to improve ad revenue.

Twitter has engaged in a number of layoffs since Musk bought the company, as the new CEO has worked to slash costs in the interest of profitability. One of the major challenges the company has faced is the loss of advertisers over some of Musk’s more controversial decisions.

Given Musk’s need to gain and keep new advertisers, one would think that ad engineers would be the one jobs safe from layoffs. Unfortunately, according to The Information, that is not the case, with some 40 ad engineers and data scientists being laid off.

The layoffs targeted areas that Twitter’s leadership considers to be failing, such as the ads product, and unimportant, such as data science, the person said. Twitter’s ad revenue has reportedly plunged in recent months, as advertisers respond to Elon Musk’s loosening of rules around content moderation and the general chaos as Musk shakes up the company.