diff --git a/actix-web/CHANGES.md b/actix-web/CHANGES.md
index 97ad926a1..6c7a448e5 100644
--- a/actix-web/CHANGES.md
+++ b/actix-web/CHANGES.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- Add `Error::add_response_mapper()` to allow middleware to modify error-generated responses before they are sent. [#2979]
+
+[#2979]: https://github.com/actix/actix-web/pull/2979
+
 ## 4.14.0
 
 - Add `HttpRequest::{cookies_raw,cookie_raw}` and `ServiceRequest::{cookies_raw,cookie_raw}` for reading request cookies without percent-decoding names and values. [#3542]
diff --git a/actix-web/README.md b/actix-web/README.md
index a83f246a3..d57941112 100644
--- a/actix-web/README.md
+++ b/actix-web/README.md
@@ -41,13 +41,9 @@
 
 ### Experimental features
 
-To enable faster release iterations, we mark some features as experimental.
-These features are prefixed with `experimental` and a breaking change may happen at any release.
-Please use them in a production environment at your own risk.
+To enable faster release iterations, we mark some features as experimental. These features are prefixed with `experimental` and a breaking change may happen at any release. Please use them in a production environment at your own risk.
 
-- `experimental-introspection`: exposes route and method reporting helpers for local diagnostics
-  and tooling. See [`examples/introspection.rs`](examples/introspection.rs) and
-  [`examples/introspection_multi_servers.rs`](examples/introspection_multi_servers.rs).
+- `experimental-introspection`: exposes route and method reporting helpers for local diagnostics and tooling. See [`examples/introspection.rs`](examples/introspection.rs) and [`examples/introspection_multi_servers.rs`](examples/introspection_multi_servers.rs).
 
 ## Documentation