diff --git a/master_changes.md b/master_changes.md
index d3be6e786fd..e287ea845c3 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -227,6 +227,7 @@ users)
   * `OpamArg.hash_kinds`: was added [#5960 @kit-ty-kate]
   * `OpamRepositoryCommand.switch_repos`: expose the function [#5014 @kit-ty-kate]
   * `OpamLockCommand.lock_opam`: add `~keep_local` argument to add local pins to pin-depends (and not resolve them) [#6411 @rjbou]
+  * `OpamLockCommand.lock_opam`: make the `?only_direct` argument non-optional [#6411 @kit-ty-kate]
 
 ## opam-repository
   * `OpamDownload.get_output`: fix `wget` option for `POST` requests [#6036 @rjbou]
diff --git a/src/client/opamCommands.ml b/src/client/opamCommands.ml
index 4030ce145e6..75959ea24b2 100644
--- a/src/client/opamCommands.ml
+++ b/src/client/opamCommands.ml
@@ -4407,7 +4407,7 @@ let lock cli =
   let lock_suffix = OpamArg.lock_suffix cli in
   let keep_local_flag =
     mk_flag ~cli (cli_from cli2_4) ["keep-local"]
-      "Do not discard local pins from pin-depends."
+      "Keep local pin paths in 'pin-depends:' field."
   in
   let lock global_options only_direct lock_suffix keep_local atom_locs () =
     apply_global_options cli global_options;
diff --git a/src/client/opamLockCommand.ml b/src/client/opamLockCommand.ml
index cd071722cc7..73515ba8fa5 100644
--- a/src/client/opamLockCommand.ml
+++ b/src/client/opamLockCommand.ml
@@ -128,7 +128,7 @@ let get_git_url url nv dir =
        (OpamPackage.to_string nv);
      None)
 
-let lock_opam ?(only_direct=false) ~keep_local st opam =
+let lock_opam ~only_direct ~keep_local st opam =
   let nv = OpamFile.OPAM.package opam in
   (* Depends *)
   let all_depends =
diff --git a/src/client/opamLockCommand.mli b/src/client/opamLockCommand.mli
index d474fd8c51c..c94cc4cbf0d 100644
--- a/src/client/opamLockCommand.mli
+++ b/src/client/opamLockCommand.mli
@@ -27,5 +27,5 @@ val select_packages:
     be resolved to a distant url are added with their local path in
     'pin_depends:' field. *)
 val lock_opam:
-  ?only_direct:bool -> keep_local:bool ->
+  only_direct:bool -> keep_local:bool ->
   'a switch_state -> OpamFile.OPAM.t -> OpamFile.OPAM.t