diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8bd18c4841..9358b9134e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@
 #### :rocket: New Feature
 
 - Add `%todo` extension for leaving implementation for later. https://github.com/rescript-lang/rescript-compiler/pull/6713
+- Add `-warn-error` argument for generate error on CI. Useful for `%todo` extension. https://github.com/rescript-lang/rescript-compiler/pull/6717
 
 #### :bug: Bug Fix
 
diff --git a/jscomp/bsb/bsb_ninja_regen.ml b/jscomp/bsb/bsb_ninja_regen.ml
index 030e98b953..d2953b93ee 100644
--- a/jscomp/bsb/bsb_ninja_regen.ml
+++ b/jscomp/bsb/bsb_ninja_regen.ml
@@ -30,7 +30,7 @@ let ( // ) = Ext_path.combine
     return None if we dont need regenerate
     otherwise return Some info
 *)
-let regenerate_ninja ~(package_kind : Bsb_package_kind.t) ~forced ~per_proj_dir ~warn_legacy_config
+let regenerate_ninja ~(package_kind : Bsb_package_kind.t) ~forced ~per_proj_dir ~warn_legacy_config ~warn_as_error
     : Bsb_config_types.t option =
   let lib_artifacts_dir = Bsb_config.lib_bs in
   let lib_bs_dir = per_proj_dir // lib_artifacts_dir in
@@ -58,6 +58,23 @@ let regenerate_ninja ~(package_kind : Bsb_package_kind.t) ~forced ~per_proj_dir
         Bsb_config_parse.interpret_json
           ~filename:config_filename ~json:config_json ~package_kind ~per_proj_dir
       in
+
+      let warning = match config.warning with
+      | None -> (
+          match warn_as_error with
+          | Some e -> Some {Bsb_warning.number = Some e; error = Warn_error_number e}
+          | None -> None)
+      | Some {error} as t ->
+          match (warn_as_error, error) with
+          | (Some error_str, Warn_error_false) ->
+              Some {number = Some error_str; error = Warn_error_number error_str}
+          | (Some error_str, Warn_error_number prev) ->
+              let new_error = prev ^ error_str in
+              Some {number = Some new_error; error = Warn_error_number new_error}
+          | _ -> t
+      in
+
+      let config = {config with warning = warning} in
       (* create directory, lib/bs, lib/js, lib/es6 etc *)
       Bsb_build_util.mkp lib_bs_dir;
       Bsb_package_specs.list_dirs_by config.package_specs (fun x ->
diff --git a/jscomp/bsb/bsb_ninja_regen.mli b/jscomp/bsb/bsb_ninja_regen.mli
index b92cf0b115..0af5766e57 100644
--- a/jscomp/bsb/bsb_ninja_regen.mli
+++ b/jscomp/bsb/bsb_ninja_regen.mli
@@ -27,6 +27,7 @@ val regenerate_ninja :
   forced:bool ->
   per_proj_dir:string ->
   warn_legacy_config:bool ->
+  warn_as_error:string option ->
   Bsb_config_types.t option
 (** Regenerate ninja file by need based on [.bsdeps]
     return None if we dont need regenerate
diff --git a/jscomp/bsb/bsb_warning.mli b/jscomp/bsb/bsb_warning.mli
index d5c3ef923d..b04fb6f038 100644
--- a/jscomp/bsb/bsb_warning.mli
+++ b/jscomp/bsb/bsb_warning.mli
@@ -22,7 +22,16 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)
 
-type t
+type warning_error =
+  | Warn_error_false
+  (* default [false] to make our changes non-intrusive *)
+  | Warn_error_true
+  | Warn_error_number of string
+
+type t0 = { number : string option; error : warning_error }
+
+type nonrec t = t0 option
+
 
 val to_merlin_string : t -> string
 (** Extra work is need to make merlin happy *)
diff --git a/jscomp/bsb/bsb_world.ml b/jscomp/bsb/bsb_world.ml
index e5e9dfdc77..30b776c796 100644
--- a/jscomp/bsb/bsb_world.ml
+++ b/jscomp/bsb/bsb_world.ml
@@ -26,7 +26,7 @@ let ( // ) = Ext_path.combine
 let vendor_ninja = Bsb_global_paths.vendor_ninja
 
 let make_world_deps cwd (config : Bsb_config_types.t option)
-    (ninja_args : string array) =
+    (ninja_args : string array) warn_as_error =
   let package_specs, jsx, uncurried, pinned_dependencies =
     match config with
     | None ->
@@ -71,6 +71,7 @@ let make_world_deps cwd (config : Bsb_config_types.t option)
                    else Dependency { package_specs; jsx; uncurried })
                  ~per_proj_dir:proj_dir ~forced:false
                  ~warn_legacy_config:false
+                 ~warn_as_error:(if is_pinned then warn_as_error else None)
              in
              let command =
                { Bsb_unix.cmd = vendor_ninja; cwd = lib_bs_dir; args }
diff --git a/jscomp/bsb/bsb_world.mli b/jscomp/bsb/bsb_world.mli
index e705a22099..123f63e5a8 100644
--- a/jscomp/bsb/bsb_world.mli
+++ b/jscomp/bsb/bsb_world.mli
@@ -23,4 +23,4 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)
 
 val make_world_deps :
-  string -> Bsb_config_types.t option -> string array -> unit
+  string -> Bsb_config_types.t option -> string array -> string option -> unit
diff --git a/jscomp/bsb_exe/rescript_main.ml b/jscomp/bsb_exe/rescript_main.ml
index c8474ee48f..3e29b33c6e 100644
--- a/jscomp/bsb_exe/rescript_main.ml
+++ b/jscomp/bsb_exe/rescript_main.ml
@@ -30,6 +30,8 @@ let no_deps_mode = ref false
 
 let do_install = ref false
 
+let warning_as_error = ref None
+
 let force_regenerate = ref false
 
 type spec = Bsb_arg.spec
@@ -40,6 +42,8 @@ let unit_set_spec b : spec = Unit (Unit_set b)
 
 let string_set_spec s : spec = String (String_set s)
 
+let string_call f: spec = String (String_call f)
+
 let failed_annon ~rev_args =
   match rev_args with
   | x :: _ -> Bsb_arg.bad_arg ("Don't know what to do with " ^ x)
@@ -132,6 +136,7 @@ let build_subcommand ~start argv argv_len =
          Always regenerate build.ninja no matter bsconfig.json is changed or \
          not" );
       ("-no-deps", unit_set_spec no_deps_mode, "*internal* Needed for watcher to build without dependencies on file change");
+      ("-warn-error", string_call (fun s -> warning_as_error := Some s), "Warning numbers and whether to turn them into errors, e.g., \"+8+32-102\"")
     |]
     failed_annon;
 
@@ -141,14 +146,20 @@ let build_subcommand ~start argv argv_len =
   match ninja_args with
   | [| "-h" |] -> ninja_command_exit ninja_args
   | _ ->
+      let warn_as_error = match !warning_as_error with
+      | Some s ->
+        let () = try Warnings.parse_options true s with Arg.Bad msg -> Bsb_arg.bad_arg (msg ^ "\n") in
+        Some s
+      | None -> None in
       let config_opt =
         Bsb_ninja_regen.regenerate_ninja
           ~package_kind:Toplevel
           ~per_proj_dir:Bsb_global_paths.cwd
           ~forced:!force_regenerate
           ~warn_legacy_config:true
+          ~warn_as_error
         in
-      if not !no_deps_mode then Bsb_world.make_world_deps Bsb_global_paths.cwd config_opt ninja_args;
+      if not !no_deps_mode then Bsb_world.make_world_deps Bsb_global_paths.cwd config_opt ninja_args warn_as_error;
       if !do_install then install_target ();
       ninja_command_exit ninja_args
 
@@ -180,6 +191,7 @@ let info_subcommand ~start argv =
             ~per_proj_dir:Bsb_global_paths.cwd
             ~forced:true
             ~warn_legacy_config:true
+            ~warn_as_error:None
         with
         | None -> assert false
         | Some { file_groups = { files } } ->
@@ -210,8 +222,9 @@ let () =
           ~per_proj_dir:Bsb_global_paths.cwd
           ~forced:false
           ~warn_legacy_config:true
+          ~warn_as_error:None
       in
-      Bsb_world.make_world_deps Bsb_global_paths.cwd config_opt [||];
+      Bsb_world.make_world_deps Bsb_global_paths.cwd config_opt [||] None;
       ninja_command_exit [||])
     else
       match argv.(1) with
diff --git a/jscomp/build_tests/build_warn_as_error/input.js b/jscomp/build_tests/build_warn_as_error/input.js
new file mode 100644
index 0000000000..878647f9d9
--- /dev/null
+++ b/jscomp/build_tests/build_warn_as_error/input.js
@@ -0,0 +1,17 @@
+var p = require("child_process");
+var assert = require("assert");
+var rescript_exe = require("../../../scripts/bin_path").rescript_exe;
+
+var o = p.spawnSync(rescript_exe, ["build", "-warn-error", "+110"], {
+  encoding: "utf8",
+  cwd: __dirname,
+});
+
+var error_message = o.stdout
+  .split("\n")
+  .map(s => s.trim())
+  .includes("Warning number 110 (configured as error)");
+
+if (!error_message) {
+  assert.fail(o.stdout);
+}
diff --git a/jscomp/build_tests/build_warn_as_error/rescript.json b/jscomp/build_tests/build_warn_as_error/rescript.json
new file mode 100644
index 0000000000..0932ebe394
--- /dev/null
+++ b/jscomp/build_tests/build_warn_as_error/rescript.json
@@ -0,0 +1,5 @@
+{
+  "name": "build_warn_as_error",
+  "version": "0.1.0",
+  "sources": ["src"]
+}
diff --git a/jscomp/build_tests/build_warn_as_error/src/Demo.res b/jscomp/build_tests/build_warn_as_error/src/Demo.res
new file mode 100644
index 0000000000..1dabe7324e
--- /dev/null
+++ b/jscomp/build_tests/build_warn_as_error/src/Demo.res
@@ -0,0 +1 @@
+let todo = _ => %todo
diff --git a/jscomp/build_tests/cli_help/input.js b/jscomp/build_tests/cli_help/input.js
index d2ebcde3c7..18c4fc7d9b 100755
--- a/jscomp/build_tests/cli_help/input.js
+++ b/jscomp/build_tests/cli_help/input.js
@@ -32,10 +32,11 @@ const buildHelp =
   "`rescript build -- -h` for Ninja options (internal usage only; unstable)\n" +
   "\n" +
   "Options:\n" +
-  "  -w          Watch mode\n" +
-  "  -ws         [host]:port set up host & port for WebSocket build notifications\n" +
-  "  -verbose    Set the output to be verbose\n" +
-  "  -with-deps  *deprecated* This is the default behavior now. This option will be removed in a future release\n";
+  "  -w           Watch mode\n" +
+  "  -ws          [host]:port set up host & port for WebSocket build notifications\n" +
+  "  -verbose     Set the output to be verbose\n" +
+  "  -with-deps   *deprecated* This is the default behavior now. This option will be removed in a future release\n" +
+  '  -warn-error  Warning numbers and whether to turn them into errors, e.g., "+8+32-102"\n';
 
 const cleanHelp =
   "Usage: rescript clean <options>\n" +