diff --git a/regsim/README.md b/regsim/README.md
index f6e54513..137b7e43 100644
--- a/regsim/README.md
+++ b/regsim/README.md
@@ -12,7 +12,6 @@ code, not all features of the W5500 will be fully simulated.
 
 All features are disabled by default.
 
-* `async`: **Nightly only.** Implement asynchronous traits.
 * `ip_in_core`: **Nightly only.** Use `core::net` networking types.
 
 ## Notes
diff --git a/regsim/src/lib.rs b/regsim/src/lib.rs
index 28a903d5..d01fd095 100644
--- a/regsim/src/lib.rs
+++ b/regsim/src/lib.rs
@@ -10,7 +10,6 @@
 //!
 //! All features are disabled by default.
 //!
-//! * `async`: **Nightly only.** Implement asynchronous traits.
 //! * `ip_in_core`: **Nightly only.** Use `core::net` networking types.
 //!
 //! # Notes