diff --git a/src/lib.rs b/src/lib.rs
index 42735383f0..7bf02f1d80 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -35,6 +35,10 @@
 //! support. This feature depends on unstable feature and requires the use of the nightly channel.
 //!
 //! - `homogeneous`. This opt-in feature enables the *experimental* homogeneous multi-core support.
+//!
+//! - `cortex-m-7`. This opt-in feature changes the `cortex-m` version from the default 0.6 to the newer 0.7. 
+//! This is to use the `InterruptNumber` trait instead of the `Nr` trait for interrupt numbers. 
+//! Enabling this feature **requires disabling the default features** (see PR #509).
 
 #![deny(missing_docs)]
 #![deny(rust_2018_compatibility)]