diff --git a/actix-http/src/h1/encoder.rs b/actix-http/src/h1/encoder.rs
index 4427174ec..bb89905fb 100644
--- a/actix-http/src/h1/encoder.rs
+++ b/actix-http/src/h1/encoder.rs
@@ -8,7 +8,7 @@ use bytes::{BufMut, BytesMut};
 
 use crate::body::BodySize;
 use crate::config::ServiceConfig;
-use crate::header::map;
+use crate::header::{map::Value, HeaderName};
 use crate::helpers;
 use crate::http::header::{CONNECTION, CONTENT_LENGTH, DATE, TRANSFER_ENCODING};
 use crate::http::{HeaderMap, StatusCode, Version};
@@ -121,21 +121,11 @@ pub(crate) trait MessageType: Sized {
             _ => {}
         }
 
-        // merging headers from head and extra headers. HeaderMap::new() does not allocate.
-        let empty_headers = HeaderMap::new();
-        let extra_headers = self.extra_headers().unwrap_or(&empty_headers);
-        let headers = self
-            .headers()
-            .inner
-            .iter()
-            .filter(|(name, _)| !extra_headers.contains_key(*name))
-            .chain(extra_headers.inner.iter());
-
         // write headers
 
         let mut has_date = false;
 
-        let mut buf = dst.chunk_mut().as_mut_ptr() as *mut u8;
+        let mut buf = dst.chunk_mut().as_mut_ptr();
         let mut remaining = dst.capacity() - dst.len();
 
         // tracks bytes written since last buffer resize
@@ -143,10 +133,10 @@ pub(crate) trait MessageType: Sized {
         // container's knowledge, this is used to sync the containers cursor after data is written
         let mut pos = 0;
 
-        for (key, value) in headers {
+        self.write_headers(|key, value| {
             match *key {
-                CONNECTION => continue,
-                TRANSFER_ENCODING | CONTENT_LENGTH if skip_len => continue,
+                CONNECTION => return,
+                TRANSFER_ENCODING | CONTENT_LENGTH if skip_len => return,
                 DATE => has_date = true,
                 _ => {}
             }
@@ -155,7 +145,7 @@ pub(crate) trait MessageType: Sized {
             let k_len = k.len();
 
             match value {
-                map::Value::One(ref val) => {
+                Value::One(ref val) => {
                     let v = val.as_ref();
                     let v_len = v.len();
 
@@ -177,7 +167,7 @@ pub(crate) trait MessageType: Sized {
 
                         // re-assign buf raw pointer since it's possible that the buffer was
                         // reallocated and/or resized
-                        buf = dst.chunk_mut().as_mut_ptr() as *mut u8;
+                        buf = dst.chunk_mut().as_mut_ptr();
                     }
 
                     // SAFETY: on each write, it is enough to ensure that the advancement of the
@@ -206,7 +196,7 @@ pub(crate) trait MessageType: Sized {
                     remaining -= len;
                 }
 
-                map::Value::Multi(ref vec) => {
+                Value::Multi(ref vec) => {
                     for val in vec {
                         let v = val.as_ref();
                         let v_len = v.len();
@@ -224,7 +214,7 @@ pub(crate) trait MessageType: Sized {
 
                             // re-assign buf raw pointer since it's possible that the buffer was
                             // reallocated and/or resized
-                            buf = dst.chunk_mut().as_mut_ptr() as *mut u8;
+                            buf = dst.chunk_mut().as_mut_ptr();
                         }
 
                         // SAFETY: on each write, it is enough to ensure that the advancement of
@@ -253,7 +243,7 @@ pub(crate) trait MessageType: Sized {
                     }
                 }
             }
-        }
+        });
 
         // final cursor synchronization with the bytes container
         //
@@ -273,6 +263,24 @@ pub(crate) trait MessageType: Sized {
 
         Ok(())
     }
+
+    fn write_headers<F>(&mut self, mut f: F)
+    where
+        F: FnMut(&HeaderName, &Value),
+    {
+        match self.extra_headers() {
+            Some(headers) => {
+                // merging headers from head and extra headers.
+                self.headers()
+                    .inner
+                    .iter()
+                    .filter(|(name, _)| !headers.contains_key(*name))
+                    .chain(headers.inner.iter())
+                    .for_each(|(k, v)| f(k, v))
+            }
+            None => self.headers().inner.iter().for_each(|(k, v)| f(k, v)),
+        }
+    }
 }
 
 impl MessageType for Response<()> {
diff --git a/src/middleware/err_handlers.rs b/src/middleware/err_handlers.rs
index dfd9a7dc5..44962aa98 100644
--- a/src/middleware/err_handlers.rs
+++ b/src/middleware/err_handlers.rs
@@ -1,10 +1,15 @@
 //! For middleware documentation, see [`ErrorHandlers`].
 
-use std::rc::Rc;
+use std::{
+    future::Future,
+    pin::Pin,
+    rc::Rc,
+    task::{Context, Poll},
+};
 
 use actix_service::{Service, Transform};
 use ahash::AHashMap;
-use futures_util::future::{ok, FutureExt, LocalBoxFuture, Ready};
+use futures_core::{future::LocalBoxFuture, ready};
 
 use crate::{
     dev::{ServiceRequest, ServiceResponse},
@@ -51,9 +56,11 @@ type ErrorHandler<B> = dyn Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse
 ///     ));
 /// ```
 pub struct ErrorHandlers<B> {
-    handlers: Rc<AHashMap<StatusCode, Box<ErrorHandler<B>>>>,
+    handlers: Handlers<B>,
 }
 
+type Handlers<B> = Rc<AHashMap<StatusCode, Box<ErrorHandler<B>>>>;
+
 impl<B> Default for ErrorHandlers<B> {
     fn default() -> Self {
         ErrorHandlers {
@@ -82,7 +89,7 @@ impl<B> ErrorHandlers<B> {
 
 impl<S, B> Transform<S, ServiceRequest> for ErrorHandlers<B>
 where
-    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
     S::Future: 'static,
     B: 'static,
 {
@@ -90,20 +97,18 @@ where
     type Error = Error;
     type Transform = ErrorHandlersMiddleware<S, B>;
     type InitError = ();
-    type Future = Ready<Result<Self::Transform, Self::InitError>>;
+    type Future = LocalBoxFuture<'static, Result<Self::Transform, Self::InitError>>;
 
     fn new_transform(&self, service: S) -> Self::Future {
-        ok(ErrorHandlersMiddleware {
-            service,
-            handlers: self.handlers.clone(),
-        })
+        let handlers = self.handlers.clone();
+        Box::pin(async move { Ok(ErrorHandlersMiddleware { service, handlers }) })
     }
 }
 
 #[doc(hidden)]
 pub struct ErrorHandlersMiddleware<S, B> {
     service: S,
-    handlers: Rc<AHashMap<StatusCode, Box<ErrorHandler<B>>>>,
+    handlers: Handlers<B>,
 }
 
 impl<S, B> Service<ServiceRequest> for ErrorHandlersMiddleware<S, B>
@@ -114,35 +119,63 @@ where
 {
     type Response = ServiceResponse<B>;
     type Error = Error;
-    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
+    type Future = ErrorHandlersFuture<S::Future, B>;
 
     actix_service::forward_ready!(service);
 
     fn call(&mut self, req: ServiceRequest) -> Self::Future {
         let handlers = self.handlers.clone();
         let fut = self.service.call(req);
+        ErrorHandlersFuture::ServiceFuture { fut, handlers }
+    }
+}
 
-        async move {
-            let res = fut.await?;
+#[pin_project::pin_project(project = ErrorHandlersProj)]
+pub enum ErrorHandlersFuture<Fut, B>
+where
+    Fut: Future,
+{
+    ServiceFuture {
+        #[pin]
+        fut: Fut,
+        handlers: Handlers<B>,
+    },
+    HandlerFuture {
+        fut: LocalBoxFuture<'static, Fut::Output>,
+    },
+}
 
-            if let Some(handler) = handlers.get(&res.status()) {
-                match handler(res) {
-                    Ok(ErrorHandlerResponse::Response(res)) => Ok(res),
-                    Ok(ErrorHandlerResponse::Future(fut)) => fut.await,
-                    Err(e) => Err(e),
+impl<Fut, B> Future for ErrorHandlersFuture<Fut, B>
+where
+    Fut: Future<Output = Result<ServiceResponse<B>, Error>>,
+{
+    type Output = Fut::Output;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        match self.as_mut().project() {
+            ErrorHandlersProj::ServiceFuture { fut, handlers } => {
+                let res = ready!(fut.poll(cx))?;
+                match handlers.get(&res.status()) {
+                    Some(handler) => match handler(res)? {
+                        ErrorHandlerResponse::Response(res) => Poll::Ready(Ok(res)),
+                        ErrorHandlerResponse::Future(fut) => {
+                            self.as_mut()
+                                .set(ErrorHandlersFuture::HandlerFuture { fut });
+                            self.poll(cx)
+                        }
+                    },
+                    None => Poll::Ready(Ok(res)),
                 }
-            } else {
-                Ok(res)
             }
+            ErrorHandlersProj::HandlerFuture { fut } => fut.as_mut().poll(cx),
         }
-        .boxed_local()
     }
 }
 
 #[cfg(test)]
 mod tests {
     use actix_service::IntoService;
-    use futures_util::future::ok;
+    use futures_util::future::{ok, FutureExt};
 
     use super::*;
     use crate::http::{header::CONTENT_TYPE, HeaderValue, StatusCode};