diff --git a/src/lib.rs b/src/lib.rs
index c9d1277..237d73f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -221,6 +221,7 @@
 //! features = ["std"]
 //! ```
 
+#![cfg_attr(not(feature = "std"), no_std)]
 #![cfg_attr(feature = "docs", feature(doc_cfg))]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
 #![allow(clippy::mutex_atomic, clippy::module_inception)]