There has been a change in newer compiler versions causing `unexpected_cfgs` to be reported in derive macros (https://github.com/rust-lang/rust/pull/132577). The warning is triggered here: https://github.com/ExpHP/npyz/blob/55f210eb5c1b6d8258ceba6c502422d95cb08d60/derive/src/lib.rs#L256 `cargo clippy` is about to remove its feature setting behavior as posted in https://blog.rust-lang.org/2024/02/28/Clippy-deprecating-feature-cargo-clippy.html I suppose the line can simply be replaced with `#[allow(clippy:useless_attribute)]`.