diff --git a/cohttp-async.opam b/cohttp-async.opam
index 5063438f35..2dbbbf9a36 100644
--- a/cohttp-async.opam
+++ b/cohttp-async.opam
@@ -26,6 +26,8 @@ depends: [
   "magic-mime"
   "logs"
   "fmt"
+  "sexplib"
+  "ppx_sexp_conv" {build & >="v0.9.0"}
   "ounit" {test}
 ]
 available: [ocaml-version >= "4.03.0"]
diff --git a/cohttp-async/src/jbuild b/cohttp-async/src/jbuild
index 461783bd73..2d3b67d1de 100644
--- a/cohttp-async/src/jbuild
+++ b/cohttp-async/src/jbuild
@@ -13,4 +13,5 @@
     ipaddr.unix
     conduit-async
     magic-mime
-    cohttp))))
+    cohttp))
+  (preprocess (pps (ppx_sexp_conv)))))
diff --git a/cohttp-lwt.opam b/cohttp-lwt.opam
index a73955bc16..776afab408 100644
--- a/cohttp-lwt.opam
+++ b/cohttp-lwt.opam
@@ -23,6 +23,8 @@ depends: [
   "jbuilder" {build & >= "1.0+beta10"}
   "cohttp"
   "lwt"
+  "sexplib"
+  "ppx_sexp_conv" {build & >="v0.9.0"}
 ]
 conflicts: [
   "lwt" {< "2.5.0"}