There has been other instances. One is as_mut_slice, which resulted in 1.15.1 patch release. https://blog.rust-lang.org/2017/02/09/Rust-1.15.1.html Another is borrow checker bug, which resulted in 1.26.2 patch release. https://blog.rust-lang.org/2018/06/05/Rust-1.26.2.html