Hillary Clinton promised on Friday that she would not cut Social Security benefits, winning praise from progressive groups that had pressured her to take such a stance — but drawing questions from Sen. Bernie Sanders (I-Vt.), who challenged her commitment to the issue.

“I won’t cut Social Security,” Clinton wrote in an initialed tweet that included a link to her campaign website’s Social Security page. “As always, I’ll defend it, & I’ll expand it. Enough false innuendos.”

The post was a response to something Sanders had tweeted earlier in the day, when he urged Clinton to “join me in saying loudly and clearly that we will never cut Social Security.”