diff --git a/README.md b/README.md
index 57ec8f276..7de7b8f8c 100644
--- a/README.md
+++ b/README.md
@@ -761,7 +761,7 @@ To avoid this problem, you can use `Eio.Exn.Backend.show`
 
 to hide the backend-specific part of errors:
 
-<!-- $MDX skip -->
+<!-- $MDX os_type<>Win32 -->
 ```ocaml
 # Eio_main.run @@ fun env ->
   let net = Eio.Stdenv.net env in
@@ -897,7 +897,7 @@ perhaps with `open_dir` to constrain all access to be within that directory.
 
 Spawning a child process can be done using the [Eio.Process][] module:
 
-<!-- $MDX non-deterministic=command -->
+<!-- $MDX os_type<>Win32 -->
 ```ocaml
 # Eio_main.run @@ fun env ->
   let proc_mgr = Eio.Stdenv.process_mgr env in
@@ -909,7 +909,7 @@ hello
 There are various optional arguments for setting the process's current directory or connecting up the standard streams.
 For example, we can use `tr` to convert some text to upper-case:
 
-<!-- $MDX non-deterministic=command -->
+<!-- $MDX os_type<>Win32 -->
 ```ocaml
 # Eio_main.run @@ fun env ->
   let proc_mgr = Eio.Stdenv.process_mgr env in
@@ -922,7 +922,7 @@ ONE TWO THREE
 If you want to capture the output of a process, you can provide a suitable `Eio.Flow.sink` as the `stdout` argument,
 or use the `parse_out` convenience wrapper:
 
-<!-- $MDX non-deterministic=command -->
+<!-- $MDX os_type<>Win32 -->
 ```ocaml
 # Eio_main.run @@ fun env ->
   let proc_mgr = Eio.Stdenv.process_mgr env in
@@ -932,7 +932,7 @@ or use the `parse_out` convenience wrapper:
 
 All process functions either return the exit status or check that it was zero (success):
 
-<!-- $MDX non-deterministic=command -->
+<!-- $MDX os_type<>Win32 -->
 ```ocaml
 # Eio_main.run @@ fun env ->
   let proc_mgr = Eio.Stdenv.process_mgr env in
diff --git a/dune-project b/dune-project
index 89d4f8809..85e56a3d0 100644
--- a/dune-project
+++ b/dune-project
@@ -28,7 +28,7 @@
   (domain-local-await (>= 0.1.0))
   (crowbar (and (>= 0.2) :with-test))
   (mtime (>= 2.0.0))
-  (mdx (and (>= 2.2.0) :with-test))
+  (mdx (and (>= 2.3.1) :with-test))
   (dscheck (and (>= 0.1.0) :with-test))))
 (package
  (name eio_linux)
@@ -38,7 +38,7 @@
  (depends
   (alcotest (and (>= 1.7.0) :with-test))
   (eio (= :version))
-  (mdx (and (>= 2.2.0) :with-test))
+  (mdx (and (>= 2.3.1) :with-test))
   (logs (>= 0.7.0))
   (fmt (>= 0.8.9))
   (cmdliner (and (>= 1.1.0) :with-test))
@@ -51,7 +51,7 @@
  (depends
   (eio (= :version))
   (iomux (>= 0.2))
-  (mdx (and (>= 2.2.0) :with-test))
+  (mdx (and (>= 2.3.1) :with-test))
   (fmt (>= 0.8.9))))
 (package
  (name eio_windows)
@@ -67,7 +67,7 @@
  (synopsis "Effect-based direct-style IO mainloop for OCaml")
  (description "Selects an appropriate Eio backend for the current platform.")
  (depends
-  (mdx (and (>= 2.2.0) :with-test))
+  (mdx (and (>= 2.3.1) :with-test))
   (kcas (and (>= 0.3.0) :with-test))
   (yojson (and (>= 2.0.2) :with-test))
   (eio_linux (and (= :version) (= :os "linux")))
diff --git a/eio.opam b/eio.opam
index 30a3b9fdb..5d47dec7e 100644
--- a/eio.opam
+++ b/eio.opam
@@ -21,7 +21,7 @@ depends: [
   "domain-local-await" {>= "0.1.0"}
   "crowbar" {>= "0.2" & with-test}
   "mtime" {>= "2.0.0"}
-  "mdx" {>= "2.2.0" & with-test}
+  "mdx" {>= "2.3.1" & with-test}
   "dscheck" {>= "0.1.0" & with-test}
   "odoc" {with-doc}
 ]
diff --git a/eio_linux.opam b/eio_linux.opam
index 94f2f56d9..a1b734a99 100644
--- a/eio_linux.opam
+++ b/eio_linux.opam
@@ -12,7 +12,7 @@ depends: [
   "dune" {>= "3.9"}
   "alcotest" {>= "1.7.0" & with-test}
   "eio" {= version}
-  "mdx" {>= "2.2.0" & with-test}
+  "mdx" {>= "2.3.1" & with-test}
   "logs" {>= "0.7.0"}
   "fmt" {>= "0.8.9"}
   "cmdliner" {>= "1.1.0" & with-test}
diff --git a/eio_main.opam b/eio_main.opam
index f152b18ea..000d98e70 100644
--- a/eio_main.opam
+++ b/eio_main.opam
@@ -10,7 +10,7 @@ doc: "https://ocaml-multicore.github.io/eio/"
 bug-reports: "https://github.com/ocaml-multicore/eio/issues"
 depends: [
   "dune" {>= "3.9"}
-  "mdx" {>= "2.2.0" & with-test}
+  "mdx" {>= "2.3.1" & with-test}
   "kcas" {>= "0.3.0" & with-test}
   "yojson" {>= "2.0.2" & with-test}
   "eio_linux" {= version & os = "linux"}
diff --git a/eio_posix.opam b/eio_posix.opam
index bba85875f..f941c1512 100644
--- a/eio_posix.opam
+++ b/eio_posix.opam
@@ -12,7 +12,7 @@ depends: [
   "dune" {>= "3.9"}
   "eio" {= version}
   "iomux" {>= "0.2"}
-  "mdx" {>= "2.2.0" & with-test}
+  "mdx" {>= "2.3.1" & with-test}
   "fmt" {>= "0.8.9"}
   "odoc" {with-doc}
 ]