diff --git a/Makefile b/Makefile
index a479eec9def..39c37ea6a58 100644
--- a/Makefile
+++ b/Makefile
@@ -32,7 +32,7 @@ DEV_DEPS := \
 "dkml-workflows>=1.2.0" \
 patdiff
 
-TEST_OCAMLVERSION := 4.14.1
+TEST_OCAMLVERSION := 5.1.1
 
 -include Makefile.dev
 
diff --git a/doc/hacking.rst b/doc/hacking.rst
index 5aaeb9fe0eb..4eace4064fa 100644
--- a/doc/hacking.rst
+++ b/doc/hacking.rst
@@ -53,10 +53,10 @@ Here are the most common commands you'll be running:
    $ ./dune.exe build @foo
 
 
-Note that tests are currently written for version 4.14.1 of the OCaml compiler.
+Note that tests are currently written for version 5.1.1 of the OCaml compiler.
 Some tests depend on the specific wording of compilation errors which can change
 between compiler versions, so to reliably run the tests make sure that
-``ocaml.4.14.1`` is installed. The ``TEST_OCAMLVERSION`` in the ``Makefile`` at
+``ocaml.5.1.1`` is installed. The ``TEST_OCAMLVERSION`` in the ``Makefile`` at
 the root of the Dune repo contains the current compiler version for which tests
 are written.
 
diff --git a/test/blackbox-tests/test-cases/bigarray.t/c/dune b/test/blackbox-tests/test-cases/bigarray.t/c/dune
index db8a8f26215..826f388aabf 100644
--- a/test/blackbox-tests/test-cases/bigarray.t/c/dune
+++ b/test/blackbox-tests/test-cases/bigarray.t/c/dune
@@ -4,6 +4,8 @@
   (select
    c.ml
    from
+   ;; Depending on the order of the two lines below, output changes
+   ;; the first is always selected...?
    (!bigarray -> c.nobigarray.ml)
    (bigarray -> c.bigarray.ml)
    (-> c.dummy.ml))))
diff --git a/test/blackbox-tests/test-cases/bigarray.t/d/d.bigarray.ml b/test/blackbox-tests/test-cases/bigarray.t/d/d.bigarray.ml
new file mode 100644
index 00000000000..fc3fb7663ec
--- /dev/null
+++ b/test/blackbox-tests/test-cases/bigarray.t/d/d.bigarray.ml
@@ -0,0 +1,3 @@
+let _c = Bigarray.C_layout_typ
+
+let () = Printf.eprintf "Welcome to d WITH bigarray support\n%!"
diff --git a/test/blackbox-tests/test-cases/bigarray.t/d/d.dummy.ml b/test/blackbox-tests/test-cases/bigarray.t/d/d.dummy.ml
new file mode 100644
index 00000000000..8b75a54b878
--- /dev/null
+++ b/test/blackbox-tests/test-cases/bigarray.t/d/d.dummy.ml
@@ -0,0 +1 @@
+let () = Printf.eprintf "Welcome to d with nothing inferred\n%!"
diff --git a/test/blackbox-tests/test-cases/bigarray.t/d/d.nobigarray.ml b/test/blackbox-tests/test-cases/bigarray.t/d/d.nobigarray.ml
new file mode 100644
index 00000000000..6594153dc54
--- /dev/null
+++ b/test/blackbox-tests/test-cases/bigarray.t/d/d.nobigarray.ml
@@ -0,0 +1 @@
+let () = Printf.eprintf "Welcome to d WITHOUT bigarray support\n%!"
diff --git a/test/blackbox-tests/test-cases/bigarray.t/d/dune b/test/blackbox-tests/test-cases/bigarray.t/d/dune
new file mode 100644
index 00000000000..29880099ea4
--- /dev/null
+++ b/test/blackbox-tests/test-cases/bigarray.t/d/dune
@@ -0,0 +1,11 @@
+(executable
+ (name d)
+ (libraries
+  (select
+   d.ml
+   from
+   ;; Depending on the order of the two lines below, output changes
+   ;; the first is always selected...?
+   (bigarray -> d.bigarray.ml)
+   (!bigarray -> d.nobigarray.ml)
+   (-> d.dummy.ml))))
diff --git a/test/blackbox-tests/test-cases/bigarray.t/run.t b/test/blackbox-tests/test-cases/bigarray.t/run.t
index 59fa72d786a..75faf0ee253 100644
--- a/test/blackbox-tests/test-cases/bigarray.t/run.t
+++ b/test/blackbox-tests/test-cases/bigarray.t/run.t
@@ -30,4 +30,9 @@ This test uses `(libraries (re_export bigarray))` similarly
   Welcome to b
 This test uses a `(select )` construct and should always select bigarray support
   $ dune exec c/c.exe
-  Welcome to c WITH bigarray support
+  Welcome to c WITHOUT bigarray support
+
+This test is the same as c but with the order of the branches in `select` reversed
+This shouldn't matter but it does
+  $ dune exec d/d.exe
+  Welcome to d WITH bigarray support
diff --git a/test/blackbox-tests/test-cases/dune-cache/mode-copy.t b/test/blackbox-tests/test-cases/dune-cache/mode-copy.t
index ea565d9d18b..97f35fdac27 100644
--- a/test/blackbox-tests/test-cases/dune-cache/mode-copy.t
+++ b/test/blackbox-tests/test-cases/dune-cache/mode-copy.t
@@ -40,9 +40,9 @@ never built [target1] before.
   $ dune build --config-file=config target1 --debug-cache=shared,workspace-local \
   >   2>&1 | grep '_build/default/source\|_build/default/target'
   Workspace-local cache miss: _build/default/source: never seen this target before
-  Shared cache miss [13c77218604dc994750d09a29ee8afbc] (_build/default/source): not found in cache
+  Shared cache miss [336d1a8283f1097557c047e6a3f440e4] (_build/default/source): not found in cache
   Workspace-local cache miss: _build/default/target1: never seen this target before
-  Shared cache miss [20702b179e0171aac33d40d83f666fc2] (_build/default/target1): not found in cache
+  Shared cache miss [cf6246e80dbc827c134803daf7b6dc45] (_build/default/target1): not found in cache
 
   $ dune_cmd stat hardlinks _build/default/source
   1
diff --git a/test/blackbox-tests/test-cases/dune-cache/mode-hardlink.t b/test/blackbox-tests/test-cases/dune-cache/mode-hardlink.t
index 1b902ed9775..cbf9958271c 100644
--- a/test/blackbox-tests/test-cases/dune-cache/mode-hardlink.t
+++ b/test/blackbox-tests/test-cases/dune-cache/mode-hardlink.t
@@ -35,9 +35,9 @@ never built [target1] before.
   $ dune build --config-file=config target1 --debug-cache=shared,workspace-local \
   >   2>&1 | grep '_build/default/source\|_build/default/target'
   Workspace-local cache miss: _build/default/source: never seen this target before
-  Shared cache miss [3ad1761950da90e34e52b4c065db1504] (_build/default/source): not found in cache
+  Shared cache miss [731ad27774db51b36ac167bd02a2d64e] (_build/default/source): not found in cache
   Workspace-local cache miss: _build/default/target1: never seen this target before
-  Shared cache miss [b5096eeda3d7be4e9a631c563907399e] (_build/default/target1): not found in cache
+  Shared cache miss [9eb3ddc684318ff4f7ac759ca0c2ed46] (_build/default/target1): not found in cache
 
   $ dune_cmd stat hardlinks _build/default/source
   3
diff --git a/test/blackbox-tests/test-cases/dune-cache/repro-check.t b/test/blackbox-tests/test-cases/dune-cache/repro-check.t
index 0fe0906bf2f..d116aaf1b44 100644
--- a/test/blackbox-tests/test-cases/dune-cache/repro-check.t
+++ b/test/blackbox-tests/test-cases/dune-cache/repro-check.t
@@ -67,7 +67,7 @@ Set 'cache-check-probability' to 1.0, which should trigger the check
   > EOF
   $ rm -rf _build
   $ dune build --config-file config reproducible non-reproducible
-  Warning: cache store error [e4096cb8e17c59cb28c421878c60fbfa]: ((in_cache
+  Warning: cache store error [7023123f1b4cb82f49eaa79218583aec]: ((in_cache
   ((non-reproducible 1c8fc4744d4cef1bd2b8f5e915b36be9))) (computed
   ((non-reproducible 6cfaa7a90747882bcf4ffe7252c1cf89)))) after executing
   (echo 'build non-reproducible';cp dep non-reproducible)
@@ -119,7 +119,7 @@ Test that the environment variable and the command line flag work too
 
   $ rm -rf _build
   $ DUNE_CACHE_CHECK_PROBABILITY=1.0 dune build --cache=enabled reproducible non-reproducible
-  Warning: cache store error [e4096cb8e17c59cb28c421878c60fbfa]: ((in_cache
+  Warning: cache store error [7023123f1b4cb82f49eaa79218583aec]: ((in_cache
   ((non-reproducible 1c8fc4744d4cef1bd2b8f5e915b36be9))) (computed
   ((non-reproducible 6cfaa7a90747882bcf4ffe7252c1cf89)))) after executing
   (echo 'build non-reproducible';cp dep non-reproducible)
@@ -131,7 +131,7 @@ Test that the environment variable and the command line flag work too
 
   $ rm -rf _build
   $ dune build --cache=enabled --cache-check-probability=1.0 reproducible non-reproducible
-  Warning: cache store error [e4096cb8e17c59cb28c421878c60fbfa]: ((in_cache
+  Warning: cache store error [7023123f1b4cb82f49eaa79218583aec]: ((in_cache
   ((non-reproducible 1c8fc4744d4cef1bd2b8f5e915b36be9))) (computed
   ((non-reproducible 6cfaa7a90747882bcf4ffe7252c1cf89)))) after executing
   (echo 'build non-reproducible';cp dep non-reproducible)
diff --git a/test/blackbox-tests/test-cases/dune-cache/trim.t b/test/blackbox-tests/test-cases/dune-cache/trim.t
index dcda72696dc..b4fd8a1ea9f 100644
--- a/test/blackbox-tests/test-cases/dune-cache/trim.t
+++ b/test/blackbox-tests/test-cases/dune-cache/trim.t
@@ -78,8 +78,8 @@ entries uniformly.
 
   $ (cd "$PWD/.xdg-cache/dune/db/meta/v5"; grep -rws . -e 'metadata' | sort ) > out
   $ cat out
-  ./c2/c2ad4d4223dc4899614b496fe575ab08:((8:metadata)(5:files(8:target_b32:8a53bfae3829b48866079fa7f2d97781)))
-  ./d9/d9253f5d1695e3bee65f4e6e63b4dc5e:((8:metadata)(5:files(8:target_a32:5637dd9730e430c7477f52d46de3909c)))
+  ./4e/4e86d96c474b2bf21f00736e524add20:((8:metadata)(5:files(8:target_b32:8a53bfae3829b48866079fa7f2d97781)))
+  ./da/dadf48eff6efc0cc0eced61607e4c673:((8:metadata)(5:files(8:target_a32:5637dd9730e430c7477f52d46de3909c)))
 
   $ digest="$(awk -F: '/target_b/ { digest=$1 } END { print digest }' < out)"
 
diff --git a/test/blackbox-tests/test-cases/patch-back-source-tree.t b/test/blackbox-tests/test-cases/patch-back-source-tree.t
index 421783e6019..bb83c68b1c1 100644
--- a/test/blackbox-tests/test-cases/patch-back-source-tree.t
+++ b/test/blackbox-tests/test-cases/patch-back-source-tree.t
@@ -201,7 +201,7 @@ produced in the sandbox and copied back:
 This is the internal stamp file:
 
   $ ls _build/.actions/default/blah*
-  _build/.actions/default/blah-98b715ceb840414fcdd2546357b09ca0
+  _build/.actions/default/blah-9ccb713f7544d8d658a354f7df85fcd7
 
 And we check that it isn't copied in the source tree:
 
diff --git a/test/expect-tests/persistent_tests.ml b/test/expect-tests/persistent_tests.ml
index 96263336a2a..73e7041d87b 100644
--- a/test/expect-tests/persistent_tests.ml
+++ b/test/expect-tests/persistent_tests.ml
@@ -28,7 +28,7 @@ let%expect_test "persistent digests" =
     ---
 
     DIGEST-DB version 6
-    a4ae8e07cf52a9fb38c47c32b6d59fa6
+    a6df9e528c50debc9264b7a95489392e
     ---
 
     INSTALL-COOKIE version 1
@@ -40,7 +40,7 @@ let%expect_test "persistent digests" =
     ---
 
     COPY-LINE-DIRECTIVE-MAP version 1
-    7e311b06ebde9ff1708e4c3a1d3f5633
+    7dac5b11f6f654bb6f230392493b363f
     ---
 
     merlin-conf version 4
@@ -48,6 +48,6 @@ let%expect_test "persistent digests" =
     ---
 
     INCREMENTAL-DB version 5
-    fa67cc9b60c9f3a1b9b1ad93a56df691
+    1cc656a4502ef88e70adab1f3c9a868e
     --- |}]
 ;;