OpenAI is pushing back the rollout of ChatGPT’s built-in image generator for free users. In a post on Wednesday, CEO Sam Altman admitted that the image-generation tool is more popular than he expected, adding that “rollout to our free tier is unfortunately going to be delayed for awhile.”

GPT-4o comes with improvements to text rendering and uses “an autoregressive approach” to image generation, which means it generates an image from left to right and top to bottom instead of all at the same time. It’s currently available to ChatGPT Plus, Pro, and Team subscribers, but now it’s not clear when it will arrive for free users.