diff --git a/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.mli b/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.mli
index 98536705..12e20fc7 100644
--- a/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.mli
+++ b/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.mli
@@ -3,6 +3,8 @@
    https://opentelemetry.io/docs/reference/specification/protocol/exporter/
    *)
 
+open Common_
+
 val get_url : unit -> string
 
 val set_url : string -> unit