diff --git a/src/utils/cli_entries.ml b/src/utils/cli_entries.ml
index c7071af56..9cca0bd66 100644
--- a/src/utils/cli_entries.ml
+++ b/src/utils/cli_entries.ml
@@ -361,6 +361,11 @@ let error fmt=
        Lwt.fail (Failure msg))
     fmt
 
+let warning fmt =
+  Format.kasprintf
+    (fun msg -> log "stderr" msg)
+    fmt
+
 let message fmt =
   Format.kasprintf
     (fun msg -> log "stdout" msg)
diff --git a/src/utils/cli_entries.mli b/src/utils/cli_entries.mli
index 209289a3b..1b431e0c8 100644
--- a/src/utils/cli_entries.mli
+++ b/src/utils/cli_entries.mli
@@ -68,6 +68,7 @@ val dispatch:
 val log_hook : (string -> string -> unit Lwt.t) option ref
 
 val error : ('a, Format.formatter, unit, 'b Lwt.t) format4 -> 'a
+val warning : ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a
 val message : ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a
 val answer : ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a
 val log : string -> ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a