diff --git a/http-svr/jbuild b/http-svr/jbuild
index 14ea686..90ede07 100644
--- a/http-svr/jbuild
+++ b/http-svr/jbuild
@@ -1,31 +1,12 @@
-(* -*- tuareg -*- *)
-#require "unix"
+(jbuild_version 1)
 
-let flags = function
-  | [] -> ""
-  | pkgs ->
-    let cmd = "ocamlfind ocamlc -verbose" ^ (
-        List.fold_left (fun acc pkg -> acc ^ " -package " ^ pkg) "" pkgs
-      ) in
-    let ic = Unix.open_process_in
-        (cmd ^ " | grep -oEe '-ppx (\"([^\"\\]|\\.)+\"|\\w+)'")
-    in
-    let rec go ic acc =
-      try go ic (acc ^ " " ^ input_line ic) with End_of_file -> close_in ic; acc
-    in
-    go ic ""
-
-
-let rewriters = ["ppx_deriving_rpc"]
-let flags = flags rewriters
-
-let () = Printf.ksprintf Jbuild_plugin.V1.send {|
 (library
  ((name httpsvr)
   (public_name http-svr)
   (wrapped false)
-  (flags (:standard -w -37-39 %s))
+  (flags (:standard -w -37-39))
   (modules (:standard \ (http_test radix_tree_test test_client test_server)))
+  (preprocess (pps (ppx_deriving_rpc)))
   (libraries (astring
               rpclib
               sha
@@ -90,4 +71,3 @@ let () = Printf.ksprintf Jbuild_plugin.V1.send {|
   (deps (test_client.exe test_server.exe client_server_test.sh))
   (action (run bash client_server_test.sh))
  ))
-|} flags