Twitter’s fourth-quarter earnings brought good news and bad news for the company as it beat estimates for revenue and earnings per share, but failed to meet Wall Street’s target for monthly active users.

The San Francisco-based company announced Thursday that it had reached 288 million monthly active users in the fourth quarter of 2014, while analysts had expected it to reach 295 million. The number of monthly active users in the last quarter was up 20 percent year-on-year, but compared to Twitter’s third-quarter results, it managed to add only four million new monthly users to its user base during the fourth quarter.

According to Twitter, Apple’s iOS 8, the iPhone maker’s new mobile operating system that was rolled out in September, cost it four million new users due to integration-related issues.

There was an “unforeseen bug in the release of iOS 8 as it related to Twitter,” Twitter CEO Dick Costolo was quoted by Bloomberg as saying, during the earnings call Thursday. “We moved on multiple fronts to minimize its impact but it wasn’t a one-size-fits-all fix.”

According to Anthony Noto, the company’s chief financial officer, Twitter lost about three million users because of a change in the Shared Links feature in the Safari browser on iOS 8.

The new iOS version does not allow the Shared Links section to automatically show tweets from Twitter followers like the iOS 7 did. As a result, users who were considered as active because of this automatic feature were then lost after they updated their devices to iOS 8, Business Insider reported. The remaining one million users that Twitter lost might have bought new iPhones and did not install the Twitter app again, or they might have forgotten their passwords and could not log back in, the Business Insider report added.

“The iOS 8 rollout had a lot of glitches, but I don’t think Twitter was being affected by the ones that got a lot of press,” Slaven Radic, CEO of app-developer consultancy Tapstream Network Inc., wrote in an e-mail to Bloomberg. “There was an intermittent Twitter-specific bug in early iOS 8 where saved Twitter accounts had to be re-authorized to work, which basically meant that users had to remove the Twitter account and re-add it.”