Slack CEO Stewart Butterfield used the company’s earnings reports to fire shots at Microsoft Teams. After losing $0.14 per share, equating to a year-on-year improvement of 58%, the company beat analyst’s expectations.

Butterfield said part of the improvement was due to the signing of a large enterprise customer, highlighting an unnamed Fortune 100 financial services firm.

“Of course, like most of our large enterprise customers, they run on Office 365,” he said. “They still chose Slack because only Slack was capable of meeting their needs. Increasingly, in regulated industries, we are seeing significant traction because Slack delivers security and compliance with scalability, an open platform and a great user experience.”

The company in question reportedly added thousands of users to its plan. Overall, Slack saw a paid user boost to over 100,000, a 37% increase from the previous year.

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However, despite its success, Slack’s stock is down 5.19% in the past 24 hours. Butterfield wasn’t as confident about the company’s future, agreeing that there were a lot of challenges from Google, Facebook, and Teams. He predicts a loss of 8 to 9 cents in the coming quarter, more than analyst expectations of 7 cents. Slack’s stocks have steadily declined from its high of $38.50 per share, which was achieved shortly after its public launch.

Butterfield previously downplayed the threat of Teams to Slack, comparing Microsoft’s tactics to Google+ and noting Bing’s lack of success.

Tens of billions of dollars into that [search engine] and I don’t know what their market share is now — 9% or something like that,” he said in July. “If the competition was based on the quality of user experience, and that’s where all the effort is, that would probably be more daunting for us.”

This is a sentiment he echoes in the earnings call, telling investors that Slack is unable to win over customers via a bundle of products and will instead continue its focus on user experience.

Despite Microsoft’s Teams late entry to the market, recent numbers suggest it has usage than Slack. In June, the tech giant revealed it has 13 million daily active users, while Slack previously stated 10 million. In 2020, Teams is set for another user boost as it replaces Skype for Business as the platform of choice for enterprise chat.