Snap CEO Evan Spiegel described as a “wakeup call” a letter from a former software engineer who described what she called a “toxic” and “sexist” culture at the Venice-based company.

In a farewell letter to employees, software engineer Shannon Lubetich criticizing the social media company for not being welcoming to women and people of color. In an interview published today by Cheddar TV, she described a party last summer in an airport hangar in Santa Monica, in which scantily clad women in costumes resembling Snapchat’s popular deer filter to passed out out appetizers and posed for photos.

Lubetich also told Cheddar TV about a senior vice president of engineering who made a penis enlargement joke while discussing a Snapchat photo manipulation filter with another male colleague. She described a “pervading sexist vibe” at the company.

“I think all of the negative things that happened to me and were said to me while I was there fueled this continuously burning fire of frustration and anger,” Lubetich told Cheddar.

Spiegel was asked to address the culture issue today at the Code Conference in Rancho Palos Verdes. He acknowledged that at a quickly growing company like Snap, it’s a challenge to reinforce the company’s culture and values.

“The wake up call with that letter is we need to do more and do it faster,” said Spiegel, who said that since the letter was written last fall the company has hired consultants to “show us areas to improve” and has reorganized its leadership team.

“I’m proud of the changes from last six months,” Spiegel said. “Obviously, there’s a lot more to do.

The executive, who seemed to have a unerring instincts about how millennials communicate, fumbled a high-profile redesign of the Snapchat app. That caused backlash from users, one million of whom signed an online petition to bring back the old version.

When celebrities like Kylie Jenner and Chrissy Teigen piled on, that battered Snap’s stock price.

In March, Snap reported its slowest daily user growth in the young company’s history. The company began tweaking its design in response to the negative feedback, and in April it began testing a revision that addressed some of users’ concerns (many found it difficult to separate messages from chats, for example).

Spiegel admitted the company will make changes that “makes people uncomfortable,” but hopes to eventually gain people’s trust that Snap is working to empower its users to express themselves with small groups of friends and be expoed to the world of content.