diff --git a/src/lib.rs b/src/lib.rs
index 0a8a1a3..6699118 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -26,6 +26,9 @@
 #![cfg_attr(feature = "nightly", doc(include = "../README.md"))]
 #![doc(html_logo_url = "https://doc.dalek.rs/assets/dalek-logo-clear.png")]
 
+//! Note that docs will only build on nightly Rust until
+//! [RFC 1990 stabilizes](https://github.com/rust-lang/rust/issues/44732).
+
 //------------------------------------------------------------------------
 // External dependencies:
 //------------------------------------------------------------------------