diff --git a/.github/workflows/build-wasm_of_ocaml.yml b/.github/workflows/build-wasm_of_ocaml.yml
index c13a33b8..3bacb9b6 100644
--- a/.github/workflows/build-wasm_of_ocaml.yml
+++ b/.github/workflows/build-wasm_of_ocaml.yml
@@ -123,7 +123,7 @@ jobs:
 
       - name: Pin dune
         run: |
-          opam pin add -n dune.3.17 https://github.com/ocaml-wasm/dune.git#wasm_of_ocaml
+          opam pin add -n dune.3.17 https://github.com/ocaml-wasm/dune.git#wasm_of_ocaml-incremental
 
       - name: Pin wasm_of_ocaml
         working-directory: ./wasm_of_ocaml
diff --git a/compiler/bin-wasm_of_ocaml/link.ml b/compiler/bin-wasm_of_ocaml/link.ml
index 11721284..7dfcbf5a 100644
--- a/compiler/bin-wasm_of_ocaml/link.ml
+++ b/compiler/bin-wasm_of_ocaml/link.ml
@@ -25,6 +25,7 @@ type t =
   ; files : string list
   ; output_file : string
   ; linkall : bool
+  ; mklib : bool
   ; enable_source_maps : bool
   }
 
@@ -53,9 +54,16 @@ let options =
     let doc = "Link all compilation units." in
     Arg.(value & flag & info [ "linkall" ] ~doc)
   in
-  let build_t common no_sourcemap sourcemap output_file files linkall =
+  let mklib =
+    let doc =
+      "Build a library (.wasma file) with the .wasmo files given on the command line. \
+       Similar to ocamlc -a."
+    in
+    Arg.(value & flag & info [ "a" ] ~doc)
+  in
+  let build_t common no_sourcemap sourcemap output_file files linkall mklib =
     let enable_source_maps = (not no_sourcemap) && sourcemap in
-    `Ok { common; output_file; files; linkall; enable_source_maps }
+    `Ok { common; output_file; files; linkall; mklib; enable_source_maps }
   in
   let t =
     Term.(
@@ -65,13 +73,14 @@ let options =
       $ sourcemap
       $ output_file
       $ files
-      $ linkall)
+      $ linkall
+      $ mklib)
   in
   Term.ret t
 
-let f { common; output_file; files; linkall; enable_source_maps } =
+let f { common; output_file; files; linkall; enable_source_maps; mklib } =
   Jsoo_cmdline.Arg.eval common;
-  Wa_link.link ~output_file ~linkall ~enable_source_maps ~files
+  Wa_link.link ~output_file ~linkall ~mklib ~enable_source_maps ~files
 
 let info =
   Info.make
diff --git a/compiler/lib/wasm/wa_link.ml b/compiler/lib/wasm/wa_link.ml
index e14c5cd3..186d4404 100644
--- a/compiler/lib/wasm/wa_link.ml
+++ b/compiler/lib/wasm/wa_link.ml
@@ -822,8 +822,126 @@ let link ~output_file ~linkall ~enable_source_maps ~files =
   if times () then Format.eprintf "    build JS runtime: %a@." Timer.print t1;
   if times () then Format.eprintf "  emit: %a@." Timer.print t
 
-let link ~output_file ~linkall ~enable_source_maps ~files =
-  try link ~output_file ~linkall ~enable_source_maps ~files
+let opt_with action x f =
+  match x with
+  | None -> f None
+  | Some x -> action x (fun y -> f (Some y))
+
+let rec get_source_map_files files src_index =
+  let z = Zip.open_in files.(!src_index) in
+  incr src_index;
+  if Zip.has_entry z ~name:"source_map.map"
+  then
+    let data = Zip.read_entry z ~name:"source_map.map" in
+    let sm = Wa_source_map.parse data in
+    if not (Wa_source_map.is_empty sm)
+    then (
+      let l = ref [] in
+      Wa_source_map.iter_sources sm (fun i j file -> l := source_name i j file :: !l);
+      if not (List.is_empty !l)
+      then z, Array.of_list (List.rev !l)
+      else (
+        Zip.close_in z;
+        get_source_map_files files src_index))
+    else (
+      Zip.close_in z;
+      get_source_map_files files src_index)
+  else get_source_map_files files src_index
+
+let add_source_map files z opt_source_map_file =
+  Option.iter
+    ~f:(fun file ->
+      Zip.add_file z ~name:"source_map.map" ~file;
+      let sm = Wa_source_map.load file in
+      let files = Array.of_list files in
+      let src_index = ref 0 in
+      let st = ref None in
+      let finalize () =
+        match !st with
+        | Some (_, (z', _)) -> Zip.close_in z'
+        | None -> ()
+      in
+      Wa_source_map.iter_sources sm (fun i j file ->
+          let z', files =
+            match !st with
+            | Some (i', st) when Poly.equal i i' -> st
+            | _ ->
+                let st' = get_source_map_files files src_index in
+                finalize ();
+                st := Some (i, st');
+                st'
+          in
+          if Array.length files > 0 (* Source has source map *)
+          then
+            let name = files.(Option.value ~default:0 j) in
+            if Zip.has_entry z' ~name
+            then Zip.copy_file z' z ~src_name:name ~dst_name:(source_name i j file));
+      finalize ())
+    opt_source_map_file
+
+let make_library ~output_file ~enable_source_maps ~files =
+  let info =
+    List.map files ~f:(fun file ->
+        let build_info, _predefined_exceptions, unit_data =
+          Zip.with_open_in file read_info
+        in
+        (match Build_info.kind build_info with
+        | `Cmo -> ()
+        | `Runtime | `Cma | `Exe | `Unknown ->
+            failwith (Printf.sprintf "File '%s' is not a .wasmo file." file));
+        file, build_info, unit_data)
+  in
+  let build_info =
+    Build_info.with_kind
+      (match info with
+      | (file, bi, _) :: r ->
+          Build_info.configure bi;
+          List.fold_left
+            ~init:bi
+            ~f:(fun bi (file', bi', _) -> Build_info.merge file bi file' bi')
+            r
+      | [] -> Build_info.create `Cma)
+      `Cma
+  in
+  let unit_data = List.concat (List.map ~f:(fun (_, _, unit_data) -> unit_data) info) in
+  Fs.gen_file output_file
+  @@ fun tmp_output_file ->
+  let z = Zip.open_out tmp_output_file in
+  add_info z ~build_info ~unit_data ();
+  (*
+- Merge all code files into a single code file (gathering source maps)
+- Copy source files
+*)
+  Fs.with_intermediate_file (Filename.temp_file "wasm" ".wasm")
+  @@ fun tmp_wasm_file ->
+  opt_with
+    Fs.with_intermediate_file
+    (if enable_source_maps then Some (Filename.temp_file "wasm" ".map") else None)
+  @@ fun opt_output_sourcemap_file ->
+  Wa_wasm_link.f
+    (List.map
+       ~f:(fun file ->
+         let z' = Zip.open_in file in
+         { Wa_wasm_link.module_name = "OCaml"
+         ; file
+         ; code = Some (Zip.read_entry z' ~name:"code.wasm")
+         ; opt_source_map =
+             (if Zip.has_entry z' ~name:"source_map.map"
+              then Some (`Data (Zip.read_entry z' ~name:"source_map.map"))
+              else None)
+         })
+       files)
+    ~output_file:tmp_wasm_file
+    ~opt_output_sourcemap_file;
+  Zip.add_file z ~name:"code.wasm" ~file:tmp_wasm_file;
+  add_source_map files z opt_output_sourcemap_file;
+  Zip.close_out z
+
+let link ~output_file ~linkall ~mklib ~enable_source_maps ~files =
+  try
+    if mklib
+    then make_library ~output_file ~enable_source_maps ~files
+    else link ~output_file ~linkall ~enable_source_maps ~files
   with Build_info.Incompatible_build_info { key; first = f1, v1; second = f2, v2 } ->
     let string_of_v = function
       | None -> "<empty>"
diff --git a/compiler/lib/wasm/wa_link.mli b/compiler/lib/wasm/wa_link.mli
index bed24894..c9bf6e5d 100644
--- a/compiler/lib/wasm/wa_link.mli
+++ b/compiler/lib/wasm/wa_link.mli
@@ -59,6 +59,7 @@ val output_js : Javascript.program -> string
 val link :
      output_file:string
   -> linkall:bool
+  -> mklib:bool
   -> enable_source_maps:bool
   -> files:string list
   -> unit