diff --git a/README.md b/README.md
index b3fb2d45..fd5f4721 100644
--- a/README.md
+++ b/README.md
@@ -159,7 +159,6 @@ The possible labels are:
 - `env=ENV` -- see the "Named execution environments" section
 - `set-VAR=VALUE` -- set an environment variable
 - `unset-VAR` -- unset an environment variable
-- `exec` -- execute this block. Only allowed when including an OCaml file.
 
 #### Shell Scripts
 
@@ -252,8 +251,6 @@ These can then be included in the document:
     ```ocaml
     ```
 
-Use the `exec` flag to execute as an OCaml block.
-
 Non-OCaml files can also be read and included in a block:
 
     <!-- $MDX file=any_file.txt -->
diff --git a/lib/block.ml b/lib/block.ml
index 460f12d1..64df66dd 100644
--- a/lib/block.ml
+++ b/lib/block.ml
@@ -30,29 +30,36 @@ let locate_errors ~loc r =
     (fun l -> List.map (fun (`Msg m) -> `Msg (locate_error_msg ~loc m)) l)
     r
 
-type ocaml_kind = Impl | Intf
+module OCaml_kind = struct
+  type t = Impl | Intf
+
+  let infer_from_file file =
+    match Filename.(remove_extension (basename file), extension file) with
+    | _, (".ml" | ".mlt" | ".eliom") -> Some Impl
+    | _, (".mli" | ".eliomi") -> Some Intf
+    | _ -> None
+end
 
 module Header = struct
-  type t = Shell of [ `Sh | `Bash ] | OCaml of ocaml_kind | Other of string
+  type t = Shell of [ `Sh | `Bash ] | OCaml | Other of string
 
   let pp ppf = function
     | Shell `Sh -> Fmt.string ppf "sh"
     | Shell `Bash -> Fmt.string ppf "bash"
-    | OCaml _ -> Fmt.string ppf "ocaml"
+    | OCaml -> Fmt.string ppf "ocaml"
     | Other s -> Fmt.string ppf s
 
   let of_string = function
     | "" -> None
     | "sh" -> Some (Shell `Sh)
     | "bash" -> Some (Shell `Bash)
-    | "ocaml" -> Some (OCaml Impl)
+    | "ocaml" -> Some OCaml
     | s -> Some (Other s)
 
   let infer_from_file file =
     match Filename.(remove_extension (basename file), extension file) with
     | ("dune" | "dune-project"), _ -> Some (Other "scheme")
-    | _, (".ml" | ".mlt" | ".eliom") -> Some (OCaml Impl)
-    | _, (".mli" | ".eliomi") -> Some (OCaml Intf)
+    | _, (".ml" | ".mli" | ".mlt" | ".eliom" | ".eliomi") -> Some OCaml
     | _, ".sh" -> Some (Shell `Sh)
     | _ -> None
 end
@@ -85,7 +92,6 @@ type ocaml_value = {
   non_det : Label.non_det option;
   errors : Output.t list;
   header : Header.t option;
-  kind : ocaml_kind;
 }
 
 type toplevel_value = { env : Ocaml_env.t; non_det : Label.non_det option }
@@ -93,6 +99,7 @@ type toplevel_value = { env : Ocaml_env.t; non_det : Label.non_det option }
 type include_ocaml_file = {
   part_included : string option;
   ocaml_value : ocaml_value option;
+  kind : OCaml_kind.t;
 }
 
 type include_other_file = { header : Header.t option }
@@ -140,8 +147,8 @@ let header t =
   | Raw { header; _ } -> header
   | OCaml { header; _ } -> header
   | Cram { language; _ } -> Some (Header.Shell language)
-  | Toplevel _ -> Some (Header.OCaml Impl)
-  | Include { file_kind = Fk_ocaml _; _ } -> Some (Header.OCaml Impl)
+  | Toplevel _ -> Some Header.OCaml
+  | Include { file_kind = Fk_ocaml _; _ } -> Some Header.OCaml
   | Include { file_kind = Fk_other b; _ } -> b.header
 
 let dump_value ppf = function
@@ -206,7 +213,7 @@ let pp_error ?syntax ?delim ppf outputs =
         outputs err_delim
   | _ -> ()
 
-let has_output t =
+let has_errors t =
   match get_ocaml_value t with
   | Some { errors = _ :: _; _ } -> true
   | _ -> false
@@ -221,7 +228,7 @@ let pp_value ?syntax ppf t =
 
 let pp_footer ?syntax ppf t =
   let delim =
-    if has_output t then (
+    if has_errors t then (
       pp_value ?syntax ppf t;
       None)
     else t.delim
@@ -392,20 +399,20 @@ let get_block_config l =
     file_inc = get_label (function File x -> Some x | _ -> None) l;
   }
 
-let mk_ocaml_value env non_det errors header ~kind =
-  { env = Ocaml_env.mk env; non_det; errors; header; kind }
+let mk_ocaml_value env non_det errors header =
+  { env = Ocaml_env.mk env; non_det; errors; header }
 
-let mk_ocaml ~loc ~config ~header ~contents ~errors ~kind =
+let mk_ocaml ~loc ~config ~header ~contents ~errors =
+  let kind = "OCaml" in
   match config with
   | { file_inc = None; part = None; env; non_det; _ } -> (
       (* TODO: why does this call guess_ocaml_kind when infer_block already did? *)
       match guess_ocaml_kind contents with
-      | `Code -> Ok (OCaml (mk_ocaml_value env non_det errors header ~kind))
+      | `Code -> Ok (OCaml (mk_ocaml_value env non_det errors header))
       | `Toplevel ->
           loc_error ~loc "toplevel syntax is not allowed in OCaml blocks.")
-  | { file_inc = Some _; _ } ->
-      label_not_allowed ~loc ~label:"file" ~kind:"OCaml"
-  | { part = Some _; _ } -> label_not_allowed ~loc ~label:"part" ~kind:"OCaml"
+  | { file_inc = Some _; _ } -> label_not_allowed ~loc ~label:"file" ~kind
+  | { part = Some _; _ } -> label_not_allowed ~loc ~label:"part" ~kind
 
 let mk_cram ~loc ?language ~config ~header ~errors () =
   let kind = "shell" in
@@ -437,31 +444,40 @@ let mk_toplevel ~loc ~config ~contents ~errors =
   | { part = Some _; _ } -> label_not_allowed ~loc ~label:"part" ~kind
 
 let mk_include ~loc ~config ~header ~errors =
+  let kind = "include" in
   match config with
   | { file_inc = Some file_included; part; non_det; env; _ } -> (
-      let* () = check_no_errors ~loc errors in
-      match header with
-      | Some (Header.OCaml k) ->
+      let kind =
+        match header with
+        | Some Header.OCaml -> `OCaml
+        | None -> (
+            match OCaml_kind.infer_from_file file_included with
+            | Some _ -> `OCaml
+            | None -> `Other)
+        | _ -> `Other
+      in
+      match kind with
+      | `OCaml ->
           let kind =
-            match Header.infer_from_file file_included with
-            | Some (Header.OCaml k') -> k'
-            | _ -> k
+            Util.Option.value ~default:OCaml_kind.Impl
+              (OCaml_kind.infer_from_file file_included)
           in
+          let part_included = part in
           let ocaml_value =
             match kind with
-            | Impl -> Some (mk_ocaml_value env non_det errors header ~kind)
+            | Impl -> Some (mk_ocaml_value env non_det errors header)
             | Intf -> None
           in
-          let file_kind = Fk_ocaml { part_included = part; ocaml_value } in
+          let file_kind = Fk_ocaml { part_included; ocaml_value; kind } in
           Ok (Include { file_included; file_kind })
-      | _ -> (
+      | `Other -> (
           match part with
           | None ->
               let file_kind = Fk_other { header } in
               Ok (Include { file_included; file_kind })
           | Some _ ->
               label_not_allowed ~loc ~label:"part" ~kind:"non-OCaml include"))
-  | { file_inc = None; _ } -> label_required ~loc ~label:"file" ~kind:"include"
+  | { file_inc = None; _ } -> label_required ~loc ~label:"file" ~kind
 
 let infer_block ~loc ~config ~header ~contents ~errors =
   match config with
@@ -470,9 +486,9 @@ let infer_block ~loc ~config ~header ~contents ~errors =
       match header with
       | Some (Header.Shell language) ->
           mk_cram ~loc ~language ~config ~header ~errors ()
-      | Some (Header.OCaml kind) -> (
+      | Some Header.OCaml -> (
           match guess_ocaml_kind contents with
-          | `Code -> mk_ocaml ~loc ~config ~header ~contents ~errors ~kind
+          | `Code -> mk_ocaml ~loc ~config ~header ~contents ~errors
           | `Toplevel -> mk_toplevel ~loc ~config ~contents ~errors)
       | _ ->
           let* () =
@@ -488,7 +504,7 @@ let mk ~loc ~section ~labels ~legacy_labels ~header ~delim ~contents ~errors =
   let config = get_block_config labels in
   let* value =
     match block_kind with
-    | Some OCaml -> mk_ocaml ~loc ~config ~header ~contents ~errors ~kind:Impl
+    | Some OCaml -> mk_ocaml ~loc ~config ~header ~contents ~errors
     | Some Cram -> mk_cram ~loc ~config ~header ~errors ()
     | Some Toplevel -> mk_toplevel ~loc ~config ~contents ~errors
     | Some Include -> mk_include ~loc ~config ~header ~errors
@@ -554,7 +570,4 @@ let is_active ?section:s t =
         | None -> Re.execp (Re.Perl.compile_pat p) "")
     | None -> true
   in
-  let executable =
-    match t.value with OCaml { kind = Intf; _ } -> false | _ -> true
-  in
-  active && t.version_enabled && t.os_type_enabled && (not t.skip) && executable
+  active && t.version_enabled && t.os_type_enabled && not t.skip
diff --git a/lib/block.mli b/lib/block.mli
index f3226185..ceafef82 100644
--- a/lib/block.mli
+++ b/lib/block.mli
@@ -16,10 +16,12 @@
 
 (** Code blocks headers. *)
 
-type ocaml_kind = Impl | Intf
+module OCaml_kind : sig
+  type t = Impl | Intf
+end
 
 module Header : sig
-  type t = Shell of [ `Sh | `Bash ] | OCaml of ocaml_kind | Other of string
+  type t = Shell of [ `Sh | `Bash ] | OCaml | Other of string
 
   val pp : Format.formatter -> t -> unit
   val of_string : string -> t option
@@ -37,7 +39,6 @@ type ocaml_value = {
   errors : Output.t list;
       (** [header] defines whether a header was specified for the block. *)
   header : Header.t option;
-  kind : ocaml_kind;
 }
 
 type toplevel_value = {
@@ -51,6 +52,7 @@ type include_ocaml_file = {
       (** [part_included] is the part of the file to synchronize with.
           If lines is not specified synchronize the whole file. *)
   ocaml_value : ocaml_value option;
+  kind : OCaml_kind.t;
 }
 
 type include_other_file = { header : Header.t option }
diff --git a/lib/mli_parser.ml b/lib/mli_parser.ml
index 65fb2fc6..e8a97766 100644
--- a/lib/mli_parser.ml
+++ b/lib/mli_parser.ml
@@ -138,7 +138,7 @@ let make_block code_block file_contents =
         Ok (header, language_label :: labels)
     | None ->
         (* If not specified, blocks are run as ocaml blocks *)
-        Ok (Some (OCaml Impl), [])
+        Ok (Some OCaml, [])
   in
   match handle_header code_block.Code_block.metadata with
   | Error _ as e -> e
diff --git a/lib/test/mdx_test.ml b/lib/test/mdx_test.ml
index 1b4171ca..a756623a 100644
--- a/lib/test/mdx_test.ml
+++ b/lib/test/mdx_test.ml
@@ -358,8 +358,10 @@ let run_exn ~non_deterministic ~silent_eval ~record_backtrace ~syntax ~silent
       match Block.value t with
       | Raw _ -> print_block ()
       | Include
-          { file_included; file_kind = Fk_ocaml { part_included; ocaml_value } }
-        ->
+          {
+            file_included;
+            file_kind = Fk_ocaml { part_included; ocaml_value; _ };
+          } ->
           assert (syntax <> Some Cram);
           let new_block =
             update_file_or_block ?root file file_included t part_included
diff --git a/test/bin/mdx-test/expect/dune.inc b/test/bin/mdx-test/expect/dune.inc
index f489a3e2..26dbaa5a 100644
--- a/test/bin/mdx-test/expect/dune.inc
+++ b/test/bin/mdx-test/expect/dune.inc
@@ -179,6 +179,18 @@
  (alias runtest)
  (action (diff errors/test-case.md errors.actual)))
 
+(rule
+ (target exec-include.actual)
+ (deps (package mdx) (source_tree exec-include))
+ (action
+  (with-stdout-to %{target}
+   (chdir exec-include
+    (run ocaml-mdx test --output - test-case.md)))))
+
+(rule
+ (alias runtest)
+ (action (diff exec-include/test-case.md exec-include.actual)))
+
 (rule
  (target exit.actual)
  (deps (package mdx) (source_tree exit))
diff --git a/test/bin/mdx-test/expect/exec-include/code.ml b/test/bin/mdx-test/expect/exec-include/code.ml
new file mode 100644
index 00000000..d407ee51
--- /dev/null
+++ b/test/bin/mdx-test/expect/exec-include/code.ml
@@ -0,0 +1,7 @@
+(* $MDX part-begin=OK *)
+let f x = x + 1
+(* $MDX part-end *)
+
+(* $MDX part-begin=KO *)
+let k = x = 1
+(* $MDX part-end *)
diff --git a/test/bin/mdx-test/expect/exec-include/code.mli b/test/bin/mdx-test/expect/exec-include/code.mli
new file mode 100644
index 00000000..da5e52f2
--- /dev/null
+++ b/test/bin/mdx-test/expect/exec-include/code.mli
@@ -0,0 +1 @@
+val f : int -> int
diff --git a/test/bin/mdx-test/expect/exec-include/test-case.md b/test/bin/mdx-test/expect/exec-include/test-case.md
new file mode 100644
index 00000000..1a120870
--- /dev/null
+++ b/test/bin/mdx-test/expect/exec-include/test-case.md
@@ -0,0 +1,34 @@
+.mli files are included but not executed:
+<!-- $MDX file=code.mli -->
+```ocaml
+val f : int -> int
+```
+
+Use `skip` to not include the .mli files:
+<!-- $MDX file=code.mli,skip -->
+```ocaml
+```
+
+.ml files are included and executed:
+<!-- $MDX file=code.ml,part=OK -->
+```ocaml
+let f x = x + 1
+```
+
+<!-- $MDX file=code.ml,part=KO -->
+```ocaml
+let k = x = 1
+```
+```mdx-error
+Line 1, characters 9-10:
+Error: Unbound value x
+```
+
+Use `skip` to not include the .ml files:
+<!-- $MDX file=code.ml,part=OK,skip -->
+```ocaml
+```
+
+<!-- $MDX file=code.ml,part=KO,skip -->
+```ocaml
+```
diff --git a/test/lib/test_block.ml b/test/lib/test_block.ml
index e2128cb5..be45ed86 100644
--- a/test/lib/test_block.ml
+++ b/test/lib/test_block.ml
@@ -14,8 +14,7 @@ let test_infer_from_file =
     make_test ~file:"dune" ~expected:(Some (Other "scheme"));
     make_test ~file:"dune-project" ~expected:(Some (Other "scheme"));
     make_test ~file:"foo.sh" ~expected:(Some (Shell `Sh));
-    make_test ~file:"foo/foo/foo.ml" ~expected:(Some (OCaml Impl));
-    make_test ~file:"foo/foo/foo.mli" ~expected:(Some (OCaml Intf));
+    make_test ~file:"foo/foo/foo.ml" ~expected:(Some OCaml);
   ]
 
 let test_mk =
@@ -40,10 +39,10 @@ let test_mk =
   in
   [
     make_test ~name:"invalid ocaml" ~labels:[ Block_kind OCaml ]
-      ~header:(Some (OCaml Impl)) ~contents:[ "# let x = 2;;" ]
+      ~header:(Some OCaml) ~contents:[ "# let x = 2;;" ]
       ~expected:(Error (`Msg "toplevel syntax is not allowed in OCaml blocks."));
     make_test ~name:"invalid toplevel" ~labels:[ Block_kind Toplevel ]
-      ~header:(Some (OCaml Impl)) ~contents:[ "let x = 2;;" ]
+      ~header:(Some OCaml) ~contents:[ "let x = 2;;" ]
       ~expected:(Error (`Msg "invalid toplevel syntax in toplevel blocks."));
   ]