diff --git a/.github/scripts/main/create-ocaml-cache.sh b/.github/scripts/main/create-ocaml-cache.sh
new file mode 100755
index 00000000000..16b5e270836
--- /dev/null
+++ b/.github/scripts/main/create-ocaml-cache.sh
@@ -0,0 +1,37 @@
+#!/bin/bash -xue
+
+OCAML_BRANCH="$1"
+PREFIX="$2"
+EXE="$3"
+OCAML_LOCAL="$4"
+PLATFORM="$5"
+
+if [[ $OCAML_BRANCH -gt 407 ]]; then
+  if [[ -n $GITHUB_BASE_REF ]]; then
+    git tag combak
+    git fetch origin $GITHUB_BASE_REF
+    git checkout origin/$GITHUB_BASE_REF
+  fi
+  make -C src_ext dune-local.stamp
+  cd src_ext/dune-local
+  ocaml bootstrap.ml
+  cp dune.exe "$PREFIX/bin/dune$EXE"
+  cd ../..
+
+  ./configure
+  make
+  cp -a _build "$OCAML_LOCAL/"
+  rm -f "$OCAML_LOCAL/_build/log"
+  mv "$OCAML_LOCAL/_build/default/src_ext" "$OCAML_LOCAL/_build/"
+  rm -rf "$OCAML_LOCAL/_build/default"/* "$OCAML_LOCAL/_build/install"
+  mv "$OCAML_LOCAL/_build/src_ext" "$OCAML_LOCAL/_build/default/" 
+  git clean -dfX
+  if [[ -n $GITHUB_BASE_REF ]]; then
+    git checkout combak
+  fi
+fi
+
+# The Windows BSD tar can't cope with symlinks, so we pre-tar the archive and cache that!
+if [[ $PLATFORM = 'Windows' ]]; then
+  tar -C "$OCAML_LOCAL" -pcf "$OCAML_LOCAL.tar" .
+fi
diff --git a/.github/scripts/main/ocaml-cache.sh b/.github/scripts/main/ocaml-cache.sh
index dd7ed0e2fab..860e51fe2df 100644
--- a/.github/scripts/main/ocaml-cache.sh
+++ b/.github/scripts/main/ocaml-cache.sh
@@ -144,32 +144,8 @@ EOF
   chmod +x "$OCAML_LOCAL/bin/ocamldoc"
 fi
 
-if [[ $OCAML_BRANCH -gt 407 ]]; then
-  if [[ -n $GITHUB_BASE_REF ]]; then
-    git tag combak
-    git fetch origin $GITHUB_BASE_REF
-    git checkout origin/$GITHUB_BASE_REF
-  fi
-  make -C src_ext dune-local.stamp
-  cd src_ext/dune-local
-  ocaml bootstrap.ml
-  cp dune.exe "$PREFIX/bin/dune$EXE"
-  cd ../..
-
-  ./configure
-  make
-  cp -a _build "$OCAML_LOCAL/"
-  rm -f "$OCAML_LOCAL/_build/log"
-  mv "$OCAML_LOCAL/_build/default/src_ext" "$OCAML_LOCAL/_build/"
-  rm -rf "$OCAML_LOCAL/_build/default"/* "$OCAML_LOCAL/_build/install"
-  mv "$OCAML_LOCAL/_build/src_ext" "$OCAML_LOCAL/_build/default/" 
-  git clean -dfX
-  if [[ -n $GITHUB_BASE_REF ]]; then
-    git checkout combak
-  fi
-fi
-
-# The Windows BSD tar can't cope with symlinks, so we pre-tar the archive and cache that!
-if [[ $PLATFORM = 'Windows' ]]; then
-  tar -C "$OCAML_LOCAL" -pcf "$OCAML_LOCAL.tar" .
-fi
+# Hand-over control to a separate script in case the branch being tested
+# updates this script, which will fail on Windows (since the script is "open"
+# and can't be overwritten)
+cp -pf .github/scripts/main/create-ocaml-cache.sh ../create-ocaml-cache.sh
+exec ../create-ocaml-cache.sh "$OCAML_BRANCH" "$PREFIX" "$EXE" "$OCAML_LOCAL" "$PLATFORM"
diff --git a/.github/workflows/ci.ml b/.github/workflows/ci.ml
index 2d4516c99b8..3570c6311ea 100644
--- a/.github/workflows/ci.ml
+++ b/.github/workflows/ci.ml
@@ -514,7 +514,7 @@ let main oc : unit =
   let keys = [
     ("archives", "archives-1-${{ hashFiles('src_ext/Makefile.sources', 'src_ext/Makefile', '.github/scripts/common/preamble.sh', '.github/scripts/main/preamble.sh', '.github/scripts/main/archives-cache.sh') }}-${{ env.OPAM_REPO_SHA }}");
     ("ocaml-secondary-compiler", "legacy-${{ env.OPAM_REPO_SHA }}");
-    ("ocaml-cache", "${{ hashFiles('.github/scripts/main/ocaml-cache.sh', '.github/scripts/main/preamble.sh') }}");
+    ("ocaml-cache", "${{ hashFiles('.github/scripts/main/ocaml-cache.sh', '.github/scripts/main/preamble.sh', '.github/scripts/main/create-ocaml-cache.sh') }}");
     ("cygwin", "${{ hashFiles('.github/scripts/cygwin.cmd') }}-${{ env.CYGWIN_EPOCH }}");
     ("opam-bs-cache", "${{ hashFiles('.github/scripts/main/opam-bs-cache.sh', '*.opam', '.github/scripts/main/preamble.sh') }}");
   ] in
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index be6b76bab98..3e71b6ee34e 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -75,8 +75,8 @@ jobs:
         echo archives=archives-1-${{ hashFiles('src_ext/Makefile.sources', 'src_ext/Makefile', '.github/scripts/common/preamble.sh', '.github/scripts/main/preamble.sh', '.github/scripts/main/archives-cache.sh') }}-${{ env.OPAM_REPO_SHA }} >> $GITHUB_OUTPUT
         echo ocaml-secondary-compiler=legacy-${{ env.OPAM_REPO_SHA }}
         echo ocaml-secondary-compiler=legacy-${{ env.OPAM_REPO_SHA }} >> $GITHUB_OUTPUT
-        echo ocaml-cache=${{ hashFiles('.github/scripts/main/ocaml-cache.sh', '.github/scripts/main/preamble.sh') }}
-        echo ocaml-cache=${{ hashFiles('.github/scripts/main/ocaml-cache.sh', '.github/scripts/main/preamble.sh') }} >> $GITHUB_OUTPUT
+        echo ocaml-cache=${{ hashFiles('.github/scripts/main/ocaml-cache.sh', '.github/scripts/main/preamble.sh', '.github/scripts/main/create-ocaml-cache.sh') }}
+        echo ocaml-cache=${{ hashFiles('.github/scripts/main/ocaml-cache.sh', '.github/scripts/main/preamble.sh', '.github/scripts/main/create-ocaml-cache.sh') }} >> $GITHUB_OUTPUT
         echo cygwin=${{ hashFiles('.github/scripts/cygwin.cmd') }}-${{ env.CYGWIN_EPOCH }}
         echo cygwin=${{ hashFiles('.github/scripts/cygwin.cmd') }}-${{ env.CYGWIN_EPOCH }} >> $GITHUB_OUTPUT
         echo opam-bs-cache=${{ hashFiles('.github/scripts/main/opam-bs-cache.sh', '*.opam', '.github/scripts/main/preamble.sh') }}