diff --git a/src/lib.rs b/src/lib.rs
index 8cbf255..cf5d72f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,6 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![cfg_attr(not(feature = "std"), no_std)]
+
 #[cfg(feature="libc")]
 #[doc(hidden)]
 pub extern crate libc;