diff --git a/compiler/bin-js_of_ocaml/cmd_arg.ml b/compiler/bin-js_of_ocaml/cmd_arg.ml
index 98d1cfee8a..8e01f358b2 100644
--- a/compiler/bin-js_of_ocaml/cmd_arg.ml
+++ b/compiler/bin-js_of_ocaml/cmd_arg.ml
@@ -308,13 +308,10 @@ let options =
         in
         Some
           ( sm_output_file
-          , { Source_map.Standard.version = 3
-            ; file
+          , { Source_map.Standard.empty with
+              file
             ; sourceroot = sourcemap_root
-            ; sources = []
             ; sources_content = (if sourcemap_don't_inline_content then None else Some [])
-            ; names = []
-            ; mappings = Source_map.Mappings.empty
             } )
       else None
     in
@@ -537,13 +534,10 @@ let options_runtime_only =
         in
         Some
           ( sm_output_file
-          , { Source_map.Standard.version = 3
-            ; file
+          , { Source_map.Standard.empty with
+              file
             ; sourceroot = sourcemap_root
-            ; sources = []
             ; sources_content = (if sourcemap_don't_inline_content then None else Some [])
-            ; names = []
-            ; mappings = Source_map.Mappings.empty
             } )
       else None
     in
diff --git a/compiler/bin-js_of_ocaml/link.ml b/compiler/bin-js_of_ocaml/link.ml
index 6b0f8add7f..09ebb39b82 100644
--- a/compiler/bin-js_of_ocaml/link.ml
+++ b/compiler/bin-js_of_ocaml/link.ml
@@ -102,13 +102,10 @@ let options =
         in
         Some
           ( sm_output_file
-          , { Source_map.Standard.version = 3
-            ; file
+          , { Source_map.Standard.empty with
+              file
             ; sourceroot = sourcemap_root
-            ; sources = []
             ; sources_content = Some []
-            ; names = []
-            ; mappings = Source_map.Mappings.empty
             } )
       else None
     in
diff --git a/compiler/lib/js_output.ml b/compiler/lib/js_output.ml
index d2f1b51991..f5198c1aa2 100644
--- a/compiler/lib/js_output.ml
+++ b/compiler/lib/js_output.ml
@@ -125,6 +125,8 @@ module Make (D : sig
 
   val get_name_index : string -> int
 
+  val hidden_location : Source_map.map
+
   val source_map_enabled : bool
 
   val accept_unnamed_var : bool
@@ -159,7 +161,7 @@ struct
          then
            match loc with
            | N | U | Pi { Parse_info.src = None | Some ""; _ } ->
-               push_mapping (PP.pos f) (Source_map.Gen { gen_line = -1; gen_col = -1 })
+               push_mapping (PP.pos f) hidden_location
            | Pi { Parse_info.src = Some file; line; col; _ } ->
                push_mapping
                  (PP.pos f)
@@ -201,10 +203,15 @@ struct
         (match loc with
         | None | Some { Parse_info.src = Some "" | None; _ } ->
             (* Use a dummy location. It is going to be ignored anyway *)
+            let ori_source =
+              match hidden_location with
+              | Source_map.Gen_Ori { ori_source; _ } -> ori_source
+              | _ -> 0
+            in
             Source_map.Gen_Ori_Name
               { gen_line = -1
               ; gen_col = -1
-              ; ori_source = 0
+              ; ori_source
               ; ori_line = 1
               ; ori_col = 0
               ; ori_name = get_name_index nm
@@ -2040,6 +2047,7 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
     | None | Some { Source_map.Standard.sources_content = None; _ } -> None
     | Some { Source_map.Standard.sources_content = Some _; _ } -> Some (ref [])
   in
+  let blackbox_file = "/builtin/blackbox.ml" in
   let push_mapping, get_file_index, get_name_index, source_map_enabled =
     let source_map_enabled =
       match source_map with
@@ -2066,7 +2074,9 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
       match Builtins.find file with
       | Some f -> Some (Builtins.File.content f)
       | None ->
-          if Sys.file_exists file && not (Sys.is_directory file)
+          if String.equal file blackbox_file
+          then Some "(* generated code *)"
+          else if Sys.file_exists file && not (Sys.is_directory file)
           then
             let content = Fs.read_file file in
             Some content
@@ -2094,6 +2104,15 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
           pos)
     , source_map_enabled )
   in
+  let hidden_location =
+    Source_map.Gen_Ori
+      { gen_line = -1
+      ; gen_col = -1
+      ; ori_source = get_file_index blackbox_file
+      ; ori_line = 1
+      ; ori_col = 0
+      }
+  in
   let module O = Make (struct
     let push_mapping = push_mapping
 
@@ -2101,6 +2120,8 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
 
     let get_file_index = get_file_index
 
+    let hidden_location = hidden_location
+
     let source_map_enabled = source_map_enabled
 
     let accept_unnamed_var = accept_unnamed_var
@@ -2128,6 +2149,11 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
               | None -> filename
               | Some _ -> Filename.concat "/builtin" filename)
         in
+        let ignore_list =
+          List.filter sources ~f:(fun filename ->
+              String.length filename >= 9
+              && String.equal (String.sub filename ~pos:0 ~len:9) "/builtin/")
+        in
         let sm_mappings = Source_map.Mappings.decode sm.mappings in
         let mappings =
           List.rev_append_map !temp_mappings sm_mappings ~f:(fun (pos, m) ->
@@ -2146,7 +2172,14 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
                     { gen_line; gen_col; ori_source; ori_line; ori_col; ori_name })
         in
         let mappings = Source_map.Mappings.encode mappings in
-        Some { sm with Source_map.Standard.sources; names; sources_content; mappings }
+        Some
+          { sm with
+            Source_map.Standard.sources
+          ; names
+          ; sources_content
+          ; mappings
+          ; ignore_list
+          }
   in
   PP.check f;
   (if stats ()
diff --git a/compiler/lib/source_map.ml b/compiler/lib/source_map.ml
index 1ae1b2f099..4dbdddd1fb 100644
--- a/compiler/lib/source_map.ml
+++ b/compiler/lib/source_map.ml
@@ -225,6 +225,11 @@ let string_of_stringlit (`Stringlit s) =
   | `String s -> s
   | _ -> invalid ()
 
+let int_of_intlit (`Intlit s) =
+  match Yojson.Safe.from_string s with
+  | `Int s -> s
+  | _ -> invalid ()
+
 let stringlit name rest : [ `Stringlit of string ] option =
   try
     match List.assoc name rest with
@@ -256,6 +261,17 @@ let list_stringlit_opt name rest =
     | _ -> invalid ()
   with Not_found -> None
 
+let list_intlit name rest =
+  try
+    match List.assoc name rest with
+    | `List l ->
+        Some
+          (List.map l ~f:(function
+              | `Intlit _ as s -> s
+              | _ -> invalid ()))
+    | _ -> invalid ()
+  with Not_found -> None
+
 module Standard = struct
   type t =
     { version : int
@@ -265,6 +281,7 @@ module Standard = struct
     ; sources_content : Source_content.t option list option
     ; names : string list
     ; mappings : Mappings.t
+    ; ignore_list : string list
     }
 
   let empty =
@@ -275,6 +292,7 @@ module Standard = struct
     ; sources_content = None
     ; names = []
     ; mappings = Mappings.empty
+    ; ignore_list = []
     }
 
   let maps ~sources_offset ~names_offset x =
@@ -400,6 +418,21 @@ module Standard = struct
                      (List.map l ~f:(function
                          | None -> `Null
                          | Some x -> Source_content.to_json x))) )
+         ; ( "ignoreList"
+           , match t.ignore_list with
+             | [] -> None
+             | _ ->
+                 Some
+                   (`List
+                     (let s = StringSet.of_list t.ignore_list in
+                      List.filter_map
+                        ~f:(fun x -> x)
+                        (List.mapi
+                           ~f:(fun i nm ->
+                             if StringSet.mem nm s
+                             then Some (`Intlit (string_of_int i))
+                             else None)
+                           t.sources))) )
          ])
 
   let of_json (json : Yojson.Raw.t) =
@@ -432,6 +465,17 @@ module Standard = struct
           | None -> Mappings.empty
           | Some s -> Mappings.of_string s
         in
+        let ignore_list =
+          let s =
+            IntSet.of_list
+              (List.map
+                 ~f:int_of_intlit
+                 (Option.value ~default:[] (list_intlit "ignoreList" rest)))
+          in
+          List.filter_map
+            ~f:(fun x -> x)
+            (List.mapi ~f:(fun i nm -> if IntSet.mem i s then Some nm else None) sources)
+        in
         { version = int_of_float (float_of_string version)
         ; file
         ; sourceroot
@@ -439,6 +483,7 @@ module Standard = struct
         ; sources_content
         ; sources
         ; mappings
+        ; ignore_list
         }
     | _ -> invalid ()
 
diff --git a/compiler/lib/source_map.mli b/compiler/lib/source_map.mli
index c00e8872b9..5db9fa0b50 100644
--- a/compiler/lib/source_map.mli
+++ b/compiler/lib/source_map.mli
@@ -79,6 +79,7 @@ module Standard : sig
           (** Left uninterpreted, since most useful operations can be performed efficiently
           directly on the encoded form, and a full decoding can be costly for big
           sourcemaps. *)
+    ; ignore_list : string list
     }
 
   val filter_map : t -> f:(int -> int option) -> t
diff --git a/compiler/tests-compiler/build_path_prefix_map.ml b/compiler/tests-compiler/build_path_prefix_map.ml
index 29f9f7c8c3..13f7cbf86c 100644
--- a/compiler/tests-compiler/build_path_prefix_map.ml
+++ b/compiler/tests-compiler/build_path_prefix_map.ml
@@ -44,5 +44,6 @@ let%expect_test _ =
     file: test.js
     sourceRoot: <none>
     sources:
+    - /builtin/blackbox.ml
     - /dune-root/test.ml
     |}]
diff --git a/compiler/tests-compiler/sourcemap.ml b/compiler/tests-compiler/sourcemap.ml
index eccd158695..4cbcbb09d2 100644
--- a/compiler/tests-compiler/sourcemap.ml
+++ b/compiler/tests-compiler/sourcemap.ml
@@ -82,14 +82,14 @@ let%expect_test _ =
        11:   (globalThis));
        12:
        13: //# sourceMappingURL=test.map
-      /dune-root/test.ml:1:0 -> 5:7
-      null -> 5:17
+      /builtin/blackbox.ml:1:0 -> 5:7
+      /builtin/blackbox.ml:1:0 -> 5:17
       /dune-root/test.ml:1:4 -> 6:12
       /dune-root/test.ml:1:7 -> 6:15
       /dune-root/test.ml:1:11 -> 6:18
       /dune-root/test.ml:1:12 -> 6:28
       /dune-root/test.ml:1:12 -> 7:7
-      null -> 7:14
+      /builtin/blackbox.ml:1:0 -> 7:14
     |}]
 
 let%expect_test _ =
diff --git a/compiler/tests-sourcemap/dump.reference b/compiler/tests-sourcemap/dump.reference
index ce5e7fd04c..5feb760f7e 100644
--- a/compiler/tests-sourcemap/dump.reference
+++ b/compiler/tests-sourcemap/dump.reference
@@ -1,5 +1,4 @@
 sourcemap for test.bc.js
-/my/sourceRoot#d.ml:1:0 -> 7:   var <>runtime = globalThis.jsoo_runtime;
 /my/sourceRoot#b.ml:1:4 -> 12:   function <>f(x){return x - 1 | 0; }
 /my/sourceRoot#b.ml:1:6 -> 14:   function f(<>x){return x - 1 | 0; }
 /my/sourceRoot#b.ml:1:10 -> 17:   function f(x){<>return x - 1 | 0; }