diff --git a/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml b/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml
index 82c4f65b..c13f2fd7 100644
--- a/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml
+++ b/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml
@@ -106,7 +106,12 @@ end = struct
     let open Cohttp in
     let headers = Header.(add_list (init ()) (Config.Env.get_headers ())) in
     let headers =
-      Header.(add headers "Content-Type" "application/x-protobuf")
+      Header.(
+        add_list headers
+          [
+            "Content-Type", "application/x-protobuf";
+            "Accept", "application/x-protobuf";
+          ])
     in
 
     let body = Cohttp_lwt.Body.of_string bod in