diff --git a/src/http_mirage_client.ml b/src/http_mirage_client.ml
index 1938e28..230cc54 100644
--- a/src/http_mirage_client.ml
+++ b/src/http_mirage_client.ml
@@ -153,7 +153,7 @@ let prepare_http_1_1_headers headers host user_pass body_length =
     | Some v -> add headers "content-length" (string_of_int v) in
   add_authentication ~add headers user_pass
 
-let single_http_1_1_request ?config flow user_pass host meth path headers body =
+let single_http_1_1_request ?config flow user_pass host meth path headers body f f_init =
   let body_length = Option.map String.length body in
   let headers = prepare_http_1_1_headers headers host user_pass body_length in
   let req = Httpaf.Request.create ~headers meth path in
@@ -163,34 +163,28 @@ let single_http_1_1_request ?config flow user_pass host meth path headers body =
     fun v ->
       if not !w then Lwt.wakeup_later notify_finished v
       ; w := true in
+  let on_eof response data () =
+    let response =
+      {
+        version= response.Httpaf.Response.version
+      ; status= (response.Httpaf.Response.status :> H2.Status.t)
+      ; reason= response.Httpaf.Response.reason
+      ; headers=
+          H2.Headers.of_list
+            (Httpaf.Headers.to_list response.Httpaf.Response.headers)
+      } in
+    wakeup (Ok (response, data))
+  in
   let response_handler response body =
-    let buf = Buffer.create 0x100 in
-    let rec on_eof () =
-      let response =
-        {
-          version= response.Httpaf.Response.version
-        ; status= (response.Httpaf.Response.status :> H2.Status.t)
-        ; reason= response.Httpaf.Response.reason
-        ; headers=
-            H2.Headers.of_list
-              (Httpaf.Headers.to_list response.Httpaf.Response.headers)
-        } in
-      wakeup (Ok (response, Some (Buffer.contents buf)))
-    and on_read ba ~off ~len =
-      Buffer.add_string buf (Bigstringaf.substring ~off ~len ba)
-      ; Httpaf.Body.schedule_read body ~on_read ~on_eof in
-    let on_eof () =
-      let response =
-        {
-          version= response.Httpaf.Response.version
-        ; status= (response.Httpaf.Response.status :> H2.Status.t)
-        ; reason= response.Httpaf.Response.reason
-        ; headers=
-            H2.Headers.of_list
-              (Httpaf.Headers.to_list response.Httpaf.Response.headers)
-        } in
-      wakeup (Ok (response, None)) in
-    Httpaf.Body.schedule_read body ~on_read ~on_eof in
+    let rec on_read on_eof data ba ~off ~len =
+      let data =
+        data >>= fun data ->
+        f data (Bigstringaf.substring ~off ~len ba)
+      in
+      Httpaf.Body.schedule_read body ~on_read:(on_read on_eof data) ~on_eof:(on_eof response data)
+    in
+    let f_init = Lwt.return f_init in
+    Httpaf.Body.schedule_read body ~on_read:(on_read on_eof f_init) ~on_eof:(on_eof response f_init) in
   let error_handler e =
     let err =
       match e with
@@ -216,7 +210,7 @@ let prepare_h2_headers headers host user_pass body_length =
       (string_of_int (Option.value ~default:0 body_length)) in
   add_authentication ~add headers user_pass
 
-let single_h2_request ?config ~scheme flow user_pass host meth path headers body
+let single_h2_request ?config ~scheme flow user_pass host meth path headers body f f_init
     =
   let body_length = Option.map String.length body in
   let headers = prepare_h2_headers headers host user_pass body_length in
@@ -227,30 +221,26 @@ let single_h2_request ?config ~scheme flow user_pass host meth path headers body
     fun v ->
       if not !w then Lwt.wakeup_later notify_finished v
       ; w := true in
+  let on_eof response data () =
+    let response =
+      {
+        version= {major= 2; minor= 0}
+      ; status= response.H2.Response.status
+      ; reason= ""
+      ; headers= response.H2.Response.headers
+      } in
+    wakeup (Ok (response, data))
+  in
   let response_handler response response_body =
-    let buf = Buffer.create 0x100 in
-    let rec on_eof () =
-      let response =
-        {
-          version= {major= 2; minor= 0}
-        ; status= response.H2.Response.status
-        ; reason= ""
-        ; headers= response.H2.Response.headers
-        } in
-      wakeup (Ok (response, Some (Buffer.contents buf)))
-    and on_read ba ~off ~len =
-      Buffer.add_string buf (Bigstringaf.substring ~off ~len ba)
-      ; H2.Body.Reader.schedule_read response_body ~on_read ~on_eof in
-    let on_eof () =
-      let response =
-        {
-          version= {major= 2; minor= 0}
-        ; status= response.H2.Response.status
-        ; reason= ""
-        ; headers= response.H2.Response.headers
-        } in
-      wakeup (Ok (response, None)) in
-    H2.Body.Reader.schedule_read response_body ~on_read ~on_eof in
+    let rec on_read on_eof data ba ~off ~len =
+      let data =
+        data >>= fun data ->
+        f data (Bigstringaf.substring ~off ~len ba)
+      in
+      H2.Body.Reader.schedule_read response_body ~on_read:(on_read on_eof data) ~on_eof:(on_eof response data)
+    in
+    let f_init = Lwt.return f_init in
+    H2.Body.Reader.schedule_read response_body ~on_read:(on_read on_eof f_init) ~on_eof:(on_eof response f_init) in
   let error_handler e =
     let err =
       match e with
@@ -319,7 +309,7 @@ let alpn_protocol_of_string = function
   | "h2" -> Some `H2
   | _ -> None
 
-let single_request ~ctx ~alpn_protocol ?config cfg ~meth ~headers ?body uri =
+let single_request ~ctx ~alpn_protocol ?config cfg ~meth ~headers ?body uri f f_init =
   Lwt.return (decode_uri ~ctx uri)
   >>? fun (ctx, scheme, host, user_pass, path) ->
   let ctx =
@@ -333,19 +323,22 @@ let single_request ~ctx ~alpn_protocol ?config cfg ~meth ~headers ?body uri =
   Mimic.resolve ctx >>? fun flow ->
   (match Option.bind (alpn_protocol flow) alpn_protocol_of_string, config with
   | (Some `HTTP_1_1 | None), Some (`HTTP_1_1 config) ->
-    single_http_1_1_request ~config flow user_pass host meth path headers body
+    single_http_1_1_request ~config flow user_pass host meth path headers body f f_init
   | (Some `HTTP_1_1 | None), None ->
-    single_http_1_1_request flow user_pass host meth path headers body
+    single_http_1_1_request flow user_pass host meth path headers body f f_init
   | (Some `H2 | None), Some (`H2 config) ->
-    single_h2_request ~config ~scheme flow user_pass host meth path headers body
+    single_h2_request ~config ~scheme flow user_pass host meth path headers body f f_init
   | Some `H2, None ->
-    single_h2_request ~scheme flow user_pass host meth path headers body
+    single_h2_request ~scheme flow user_pass host meth path headers body f f_init
   | Some `H2, Some (`HTTP_1_1 _) ->
-    single_h2_request ~scheme flow user_pass host meth path headers body
+    single_h2_request ~scheme flow user_pass host meth path headers body f f_init
   | Some `HTTP_1_1, Some (`H2 _) ->
-    single_http_1_1_request flow user_pass host meth path headers body)
+    single_http_1_1_request flow user_pass host meth path headers body f f_init)
   >>= fun r ->
-  Mimic.close flow >|= fun () -> r
+  Mimic.close flow >>= fun () ->
+  match r with
+  | Error _ as e -> Lwt.return e
+  | Ok (resp, body) -> Lwt.map (fun body -> Ok (resp, body)) body
 
 let tls_config ?tls_config ?config authenticator user's_authenticator =
   lazy
@@ -378,7 +371,7 @@ let resolve_location ~uri ~location =
     | _ -> Error (`Msg ("expected an absolute uri, got: " ^ uri)))
   | _ -> Error (`Msg ("unknown location (relative path): " ^ location))
 
-let one_request
+let request
     ?config
     ?tls_config:cfg
     {ctx; alpn_protocol; authenticator}
@@ -388,18 +381,20 @@ let one_request
     ?body
     ?(max_redirect = 5)
     ?(follow_redirect = true)
-    uri =
+    uri
+    f
+    f_init =
   let tls_config =
     tls_config ?tls_config:cfg ?config authenticator user's_authenticator in
   if not follow_redirect then
     single_request ~ctx ~alpn_protocol ?config tls_config ~meth ~headers ?body
-      uri
+      uri f f_init
   else
     let rec follow_redirect count uri =
       if count = 0 then Lwt.return_error (`Msg "Redirect limit exceeded")
       else
         single_request ~ctx ~alpn_protocol ?config tls_config ~meth ~headers
-          ?body uri
+          ?body uri f f_init
         >>? fun (resp, body) ->
         if Status.is_redirection resp.status then
           match Headers.get resp.headers "location" with
diff --git a/src/http_mirage_client.mli b/src/http_mirage_client.mli
index 2baf154..e15da90 100644
--- a/src/http_mirage_client.mli
+++ b/src/http_mirage_client.mli
@@ -22,7 +22,7 @@ type response = {
   ; headers: Headers.t
 }
 
-val one_request :
+val request :
      ?config:[ `H2 of H2.Config.t | `HTTP_1_1 of Httpaf.Config.t ]
   -> ?tls_config:Tls.Config.client
   -> t
@@ -33,4 +33,6 @@ val one_request :
   -> ?max_redirect:int
   -> ?follow_redirect:bool
   -> string
-  -> (response * string option, [> Mimic.error ]) result Lwt.t
+  -> ('a -> string -> 'a Lwt.t)
+  -> 'a
+  -> (response * 'a, [> Mimic.error ]) result Lwt.t