diff --git a/doc/reference/dune/executable.rst b/doc/reference/dune/executable.rst
index 39111b274294..9fad1969f56a 100644
--- a/doc/reference/dune/executable.rst
+++ b/doc/reference/dune/executable.rst
@@ -297,7 +297,7 @@ options using ``(wasm_of_ocaml (<wasm_of_ocaml-options>))``.
 - ``(wasm_files (<files-list>))`` to specify ``wasm_of_ocaml``
   Wasm runtime files.
 
-For the ``(sourcemap <config>)`` option, source maps are generated when ``<config>>`` is either ``file`` or ``inline``. They are put within the ``.bc.wasm.assets``  directory in both cases.
+For the ``(sourcemap <config>)`` option, ``<config>`` must be one of ``no`` or ``inline``. Source maps are put within the ``.bc.wasm.assets``  directory.
 
 The default values for ``flags``, ``compilation_mode`` and ``sourcemap`` depend on the selected build profile. The
 build profile ``dev`` (the default) will enable sourcemaps, separate compilation and pretty Wasm output.
diff --git a/src/dune_rules/dune_env.ml b/src/dune_rules/dune_env.ml
index 7411f9b2d681..b0aeffb4808e 100644
--- a/src/dune_rules/dune_env.ml
+++ b/src/dune_rules/dune_env.ml
@@ -225,14 +225,14 @@ let js_of_ocaml_field =
   field
     "js_of_ocaml"
     ~default:Js_of_ocaml.Env.empty
-    (Dune_lang.Syntax.since Stanza.syntax (3, 0) >>> Js_of_ocaml.Env.decode)
+    (Dune_lang.Syntax.since Stanza.syntax (3, 0) >>> Js_of_ocaml.Env.decode ~mode:JS)
 ;;
 
 let wasm_of_ocaml_field =
   field
     "wasm_of_ocaml"
     ~default:Js_of_ocaml.Env.empty
-    (Dune_lang.Syntax.since Stanza.syntax (3, 17) >>> Js_of_ocaml.Env.decode)
+    (Dune_lang.Syntax.since Stanza.syntax (3, 17) >>> Js_of_ocaml.Env.decode ~mode:Wasm)
 ;;
 
 let bin_annot = field_o "bin_annot" (Dune_lang.Syntax.since Stanza.syntax (3, 8) >>> bool)
diff --git a/src/dune_rules/jsoo/js_of_ocaml.ml b/src/dune_rules/jsoo/js_of_ocaml.ml
index 40b21d5eb530..9411c647efc9 100644
--- a/src/dune_rules/jsoo/js_of_ocaml.ml
+++ b/src/dune_rules/jsoo/js_of_ocaml.ml
@@ -74,7 +74,11 @@ module Sourcemap = struct
     | Inline
     | File
 
-  let decode = enum [ "no", No; "inline", Inline; "file", File ]
+  let decode ~mode =
+    match (mode : Mode.t) with
+    | JS -> enum [ "no", No; "inline", Inline; "file", File ]
+    | Wasm -> enum [ "no", No; "inline", Inline ]
+  ;;
 
   let equal x y =
     match x, y with
@@ -232,7 +236,7 @@ module In_buildable = struct
            only_in_executable
              (field_o
                 "sourcemap"
-                (Dune_lang.Syntax.since Stanza.syntax (3, 17) >>> Sourcemap.decode))
+                (Dune_lang.Syntax.since Stanza.syntax (3, 17) >>> Sourcemap.decode ~mode))
          in
          { flags; enabled_if; javascript_files; wasm_files; compilation_mode; sourcemap }))
   ;;
@@ -301,13 +305,13 @@ module Env = struct
     ; enabled_if : Blang.t option
     }
 
-  let decode =
+  let decode ~mode =
     fields
     @@ let+ compilation_mode = field_o "compilation_mode" Compilation_mode.decode
        and+ sourcemap =
          field_o
            "sourcemap"
-           (Dune_lang.Syntax.since Stanza.syntax (3, 17) >>> Sourcemap.decode)
+           (Dune_lang.Syntax.since Stanza.syntax (3, 17) >>> Sourcemap.decode ~mode)
        and+ runtest_alias = field_o "runtest_alias" Dune_lang.Alias.decode
        and+ flags = Flags.decode
        and+ enabled_if =
diff --git a/src/dune_rules/jsoo/js_of_ocaml.mli b/src/dune_rules/jsoo/js_of_ocaml.mli
index 2201ecee6c39..82e590835fab 100644
--- a/src/dune_rules/jsoo/js_of_ocaml.mli
+++ b/src/dune_rules/jsoo/js_of_ocaml.mli
@@ -127,7 +127,7 @@ module Env : sig
 
   val map : f:('a -> 'b) -> 'a t -> 'b t
   val equal : Ordered_set_lang.Unexpanded.t t -> Ordered_set_lang.Unexpanded.t t -> bool
-  val decode : Ordered_set_lang.Unexpanded.t t Dune_lang.Decoder.t
+  val decode : mode:Mode.t -> Ordered_set_lang.Unexpanded.t t Dune_lang.Decoder.t
   val default : profile:Profile.t -> string list t
   val empty : Ordered_set_lang.Unexpanded.t t
 end
diff --git a/src/dune_rules/jsoo/jsoo_rules.ml b/src/dune_rules/jsoo/jsoo_rules.ml
index 79399ac1bdf0..c20e4d776678 100644
--- a/src/dune_rules/jsoo/jsoo_rules.ml
+++ b/src/dune_rules/jsoo/jsoo_rules.ml
@@ -259,12 +259,14 @@ let js_of_ocaml_rule
        | Compile -> S []
        | Link -> A "link"
        | Build_runtime -> A "build-runtime")
-    ; (match (sourcemap : Js_of_ocaml.Sourcemap.t), mode with
-       | No, _ -> A "--no-source-map"
-       | Inline, _ | File, Wasm ->
-         (* With wasm_of_ocaml, source maps are always inline *)
-         A "--source-map-inline"
-       | File, JS ->
+    ; (match (sourcemap : Js_of_ocaml.Sourcemap.t) with
+       | No -> A "--no-source-map"
+       | Inline -> A "--source-map-inline"
+       | File ->
+         assert (
+           match mode with
+           | JS -> true
+           | Wasm -> false);
          S
            [ A "--source-map"
            ; Hidden_targets [ Path.Build.set_extension target ~ext:".map" ]