diff --git a/mbedtls-platform-support/src/lib.rs b/mbedtls-platform-support/src/lib.rs
index 5ccbd2952..b95726360 100644
--- a/mbedtls-platform-support/src/lib.rs
+++ b/mbedtls-platform-support/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(not(feature = "std"))]
 #[allow(unused)]
 #[macro_use]