diff --git a/Cargo.lock b/Cargo.lock
index 572f13a..e8498b6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3553,8 +3553,9 @@ dependencies = [
 name = "middleware-ext-mut"
 version = "0.1.0"
 dependencies = [
- "actix-web 3.3.3",
+ "actix-web 4.0.0-beta.21",
  "env_logger 0.9.0",
+ "log",
 ]
 
 [[package]]
diff --git a/basics/middleware-ext-mut/Cargo.toml b/basics/middleware-ext-mut/Cargo.toml
index 9cfd3a8..fdd58a8 100644
--- a/basics/middleware-ext-mut/Cargo.toml
+++ b/basics/middleware-ext-mut/Cargo.toml
@@ -5,6 +5,6 @@ authors = ["Eric McCarthy <ericmccarthy7@gmail.com>"]
 edition = "2018"
 
 [dependencies]
-actix-web = "3"
-
+actix-web = "4.0.0-beta.21"
+log = "0.4"
 env_logger = "0.9"
diff --git a/basics/middleware-ext-mut/README.md b/basics/middleware-ext-mut/README.md
index f16a1f2..66bdbcf 100644
--- a/basics/middleware-ext-mut/README.md
+++ b/basics/middleware-ext-mut/README.md
@@ -1,6 +1,6 @@
 # middleware examples
 
-This example showcases a middleware that adds and retreives request-local data. See also the [Middleware guide](https://actix.rs/docs/middleware/).
+This example showcases a middleware that adds and retrieves request-local data. See also the [Middleware guide](https://actix.rs/docs/middleware/).
 
 ## Usage
 
diff --git a/basics/middleware-ext-mut/src/add_msg.rs b/basics/middleware-ext-mut/src/add_msg.rs
index cc0a03d..e8e36e3 100644
--- a/basics/middleware-ext-mut/src/add_msg.rs
+++ b/basics/middleware-ext-mut/src/add_msg.rs
@@ -1,11 +1,13 @@
 use std::{
-    future::{ready, Future, Ready},
-    pin::Pin,
+    future::{ready, Ready},
     task::{Context, Poll},
 };
 
-use actix_web::dev::{Service, ServiceRequest, ServiceResponse, Transform};
 use actix_web::Error;
+use actix_web::{
+    dev::{Service, ServiceRequest, ServiceResponse, Transform},
+    HttpMessage,
+};
 
 #[derive(Debug, Clone)]
 pub struct Msg(pub String);
@@ -16,43 +18,28 @@ pub struct AddMsgService<S> {
     enabled: bool,
 }
 
-impl<S, B> Service for AddMsgService<S>
+impl<S, B> Service<ServiceRequest> for AddMsgService<S>
 where
-    S: Service<
-        Request = ServiceRequest,
-        Response = ServiceResponse<B>,
-        Error = actix_web::Error,
-    >,
-    S::Future: 'static,
-    B: 'static,
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error>,
 {
-    type Request = ServiceRequest;
     type Response = ServiceResponse<B>;
     type Error = Error;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Error>>>>;
+    type Future = S::Future;
 
-    fn poll_ready(&mut self, ctx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+    fn poll_ready(&self, ctx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         self.service.poll_ready(ctx)
     }
 
-    fn call(&mut self, req: Self::Request) -> Self::Future {
-        println!("request is passing through the AddMsg middleware");
-
-        // get mut HttpRequest from ServiceRequest
-        let (request, pl) = req.into_parts();
+    fn call(&self, req: ServiceRequest) -> Self::Future {
+        log::info!("request is passing through the AddMsg middleware");
 
         if self.enabled {
             // insert data into extensions if enabled
-            request
-                .extensions_mut()
+            req.extensions_mut()
                 .insert(Msg("Hello from Middleware!".to_owned()));
         }
 
-        // construct a new service response
-        match ServiceRequest::from_parts(request, pl) {
-            Ok(req) => Box::pin(self.service.call(req)),
-            Err(_) => Box::pin(ready(Err(Error::from(())))),
-        }
+        self.service.call(req)
     }
 }
 
@@ -71,17 +58,10 @@ impl AddMsg {
     }
 }
 
-impl<S, B> Transform<S> for AddMsg
+impl<S, B> Transform<S, ServiceRequest> for AddMsg
 where
-    S: Service<
-        Request = ServiceRequest,
-        Response = ServiceResponse<B>,
-        Error = actix_web::Error,
-    >,
-    S::Future: 'static,
-    B: 'static,
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error>,
 {
-    type Request = ServiceRequest;
     type Response = ServiceResponse<B>;
     type Error = Error;
     type Future = Ready<Result<Self::Transform, Self::InitError>>;