Twitter is no longer pointing the finger at Apple’s iOS8 update for a loss of users, following comments made by CEO Dick Costolo in its Q4 investors’ call.

“To clarify from yesterday’s call: there was no bug or issue with iOS 8. It is an issue on Twitter’s side as users upgraded,” the company tweeted.

Costolo said during the Q4 investors’ call that the iOS8 upgrade wiped one million Twitter users because they either forgot their password or did not download the app after updating their software.

On a conference call with analysts, Costolo blamed “an unforeseen bug in the release of iOS8” as it related to the Twitter integration for this particular loss.

He said a further three million Twitter users were lost after Apple changed a feature called Shared Links in the latest version of the Safari mobile browser in iOS8.

Costolo also admitted during the call that seasonality played a role. Q4 is slower than other three-month periods for new users.

Still, the effect was striking and caused questions from analysts. Twitter’s run rate for net additions in recent quarters has been 13 million (Q3, 2014), 16 million (Q2 2014) and 14 million (Q1 2014) monthly active users (MAUs). The Q4 2014 figure was only four million.

It now has a total of 288 million MAUs.

Otherwise, the company was upbeat on earnings and revenue, where it beat expectations. Q4 revenue nearly doubled to $479 million from the same period in 2013. And the net loss fell to $125 million from $511 million in Q4 2013.