-#![cfg_attr(all(any(test, feature = "_test_utils"), feature = "unstable"), feature(test))]
-#[cfg(all(any(test, feature = "_test_utils"), feature = "unstable"))] extern crate test;
+#![cfg_attr(all(any(test, feature = "_test_utils"), feature = "_bench_unstable"), feature(test))]
+#[cfg(all(any(test, feature = "_test_utils"), feature = "_bench_unstable"))] extern crate test;
+
+#[cfg(not(any(feature = "std", feature = "no-std")))]
+compile_error!("at least one of the `std` or `no-std` features must be enabled");