diff --git a/Makefile b/Makefile
index 499085d..2428bca 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,8 @@ clean:
 doc:
 	@dune build @doc
 
+WATCH?=@all
 watch:
-	@dune build @all -w
+	@dune build $(WATCH )-w
 
 .PHONY: all build test watch
diff --git a/src/core/Ezcurl_core.ml b/src/core/Ezcurl_core.ml
index f465e03..5e573a0 100644
--- a/src/core/Ezcurl_core.ml
+++ b/src/core/Ezcurl_core.ml
@@ -311,15 +311,21 @@ module Make(IO : IO)
     in
     _apply_config self config;
     opt_iter range ~f:(fun s -> Curl.set_range self s);
+
     (* TODO: ability to make content a stream with a `read` function *)
     opt_iter content
       ~f:(fun content ->
         Curl.set_readfunction self (content_read_fun_ content);
         (* also set size if known *)
-        match content_size_ content with
-        | None -> headers := ("transfer-encoding", "chunked") :: !headers
-        | Some size -> Curl.set_infilesize self size
+        match content_size_ content, meth with
+        | None, _ ->
+            headers := ("expect", "") :: ("transfer-encoding", "chunked") :: !headers
+        | Some size , POST _ ->
+            Curl.set_postfieldsize self size;
+        | Some size, _ ->
+            Curl.set_infilesize self size
         );
+
     (* local state *)
     let tries = max tries 1 in (* at least one attempt *)
     let body = Buffer.create 64 in
@@ -329,7 +335,8 @@ module Make(IO : IO)
     begin match meth with
       | POST [] when (content <> None) ->
         Curl.set_post self true
-      | POST l -> Curl.set_httppost self l;
+      | POST l ->
+          Curl.set_httppost self l;
       | GET -> Curl.set_httpget self true;
       | PUT ->
           Curl.set_customrequest self "PUT";
@@ -341,6 +348,7 @@ module Make(IO : IO)
       | TRACE -> Curl.set_customrequest self "TRACE"
       | PATCH -> Curl.set_customrequest self "PATCH"
     end;
+
     _set_headers self !headers;
     Curl.set_headerfunction self
       (fun s0 ->