diff --git a/src/gen_rules.ml b/src/gen_rules.ml
index 0f716d04..7adb32ea 100644
--- a/src/gen_rules.ml
+++ b/src/gen_rules.ml
@@ -1398,48 +1398,19 @@ module Gen(P : Params) = struct
   let ocamllex_rules (conf : Ocamllex.t) ~dir =
     List.iter conf.names ~f:(fun name ->
       let src = Path.relative dir (name ^ ".mll"   ) in
-      let tmp = Path.relative dir (name ^ ".tmp.ml") in
       let dst = Path.relative dir (name ^ ".ml"    ) in
       add_rule
-        (Build.run (Dep ctx.ocamllex) [A "-q"; A "-o"; Path tmp; Dep src]
-         >>>
-         Build.create_file ~target:dst (fun () ->
-           let repl = Path.to_string (Path.append ctx.build_dir dst) in
-           let tmp = Path.to_string tmp in
-           let dst = Path.to_string dst in
-           Rewrite_generated_file.rewrite ~src:tmp ~dst ~repl;
-           Sys.remove tmp)))
+        (Build.run (Dep ctx.ocamllex) [A "-q"; A "-o"; Target dst; Dep src]))
 
   let ocamlyacc_rules (conf : Ocamlyacc.t) ~dir =
     List.iter conf.names ~f:(fun name ->
       let src  = Path.relative dir (name ^ ".mly"    ) in
-      let tmp  = Path.relative dir (name ^ ".tmp.ml" ) in
-      let tmpi = Path.relative dir (name ^ ".tmp.mli") in
       let dst  = Path.relative dir (name ^ ".ml"     ) in
       let dsti = Path.relative dir (name ^ ".mli"    ) in
       add_rule
-        (Build.run
+        (Build.run ~extra_targets:[dst; dsti]
            (Dep ctx.ocamlyacc)
-           [ A "-b"
-           ; Path (Path.relative dir (name ^ ".tmp"))
-           ; Dep src
-           ]
-         >>>
-         Build.create_files ~targets:[dst; dsti] (fun () ->
-           let repl = Path.to_string (Path.append ctx.build_dir dst) in
-           let tmp = Path.to_string tmp in
-           let dst = Path.to_string dst in
-           Rewrite_generated_file.rewrite ~src:tmp ~dst ~repl;
-           Sys.remove tmp;
-
-           let repli = Path.to_string (Path.append ctx.build_dir dsti) in
-           let tmpi = Path.to_string tmpi in
-           let dsti = Path.to_string dsti in
-           with_file_in tmpi ~f:(fun ic ->
-             with_file_out dsti ~f:(fun oc ->
-               Printf.fprintf oc "# 1 \"%s\"\n" repli;
-               copy_channels ic oc));
-           Sys.remove tmpi)))
+           [ Dep src ]))
 
   (* +-----------------------------------------------------------------+
      | Modules listing                                                 |
diff --git a/src/jbuild b/src/jbuild
index 47c1fa25..77156ac4 100644
--- a/src/jbuild
+++ b/src/jbuild
@@ -5,4 +5,4 @@
   (public_name jbuilder)
   (libraries   (unix jbuilder_re))))
 
-(ocamllex (sexp_lexer meta_lexer rewrite_generated_file glob_lexer))
+(ocamllex (sexp_lexer meta_lexer glob_lexer))
diff --git a/src/rewrite_generated_file.mli b/src/rewrite_generated_file.mli
deleted file mode 100644
index b85e581b..00000000
--- a/src/rewrite_generated_file.mli
+++ /dev/null
@@ -1 +0,0 @@
-val rewrite : src:string -> dst:string -> repl:string -> unit
diff --git a/src/rewrite_generated_file.mll b/src/rewrite_generated_file.mll
deleted file mode 100644
index 872ba0a9..00000000
--- a/src/rewrite_generated_file.mll
+++ /dev/null
@@ -1,20 +0,0 @@
-{ open Import }
-
-rule iter src repl oc = parse
-  | ("# " ['0'-'9']+ " \"" as before) ([^'"' '\n']* as name) ('"' '\r'? '\n' as after)
-    { output_string oc before;
-      output_string oc (if name = src then repl else name);
-      output_string oc after;
-      iter src repl oc lexbuf }
-  | [^'\n']* '\n' as s
-    { output_string oc s;
-      iter src repl oc lexbuf }
-  | [^'\n']* eof as s
-    { output_string oc s }
-
-{
-  let rewrite ~src ~dst ~repl =
-    with_file_in src ~f:(fun ic ->
-      with_file_out dst ~f:(fun oc ->
-        iter src repl oc (Lexing.from_channel ic)))
-}