diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 5c63d1d4a..cec49d559 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -30,7 +30,7 @@ concurrency:
 jobs:
   coverage:
     name: "${{ matrix.python-version }} on ${{ matrix.os }}"
-    runs-on: "${{ matrix.os }}-latest"
+    runs-on: "${{ matrix.os }}-${{ matrix.os-version || 'latest' }}"
     env:
       MATRIX_ID: "${{ matrix.python-version }}.${{ matrix.os }}"
 
@@ -69,6 +69,15 @@ jobs:
             python-version: "pypy-3.9"
           - os: windows
             python-version: "pypy-3.10"
+        # GitHub is rolling out macos 14, but it doesn't have Python 3.8 or 3.9.
+        # https://mastodon.social/@hugovk/112320493602782374
+        include:
+          - python-version: "3.8"
+            os: "macos"
+            os-version: "13"
+          - python-version: "3.9"
+            os: "macos"
+            os-version: "13"
       # If one job fails, stop the whole thing.
       fail-fast: true
 
diff --git a/.github/workflows/kit.yml b/.github/workflows/kit.yml
index 9d78b430e..36a1d42bd 100644
--- a/.github/workflows/kit.yml
+++ b/.github/workflows/kit.yml
@@ -48,7 +48,7 @@ concurrency:
 jobs:
   wheels:
     name: "${{ matrix.py }} ${{ matrix.os }} ${{ matrix.arch }} wheels"
-    runs-on: ${{ matrix.os }}-latest
+    runs-on: "${{ matrix.os }}-${{ matrix.os-version || 'latest' }}"
     env:
       MATRIX_ID: "${{ matrix.py }}-${{ matrix.os }}-${{ matrix.arch }}"
     strategy:
@@ -84,7 +84,7 @@ jobs:
           #
           #   # Some OS/arch combinations need overrides for the Python versions:
           #   os_arch_pys = {
-          #     ("macos", "arm64"): ["cp38", "cp39", "cp310", "cp311", "cp312"],
+          #     # ("macos", "arm64"): ["cp38", "cp39", "cp310", "cp311", "cp312"],
           #   }
           #
           #   #----- ^^^ ---------------------- ^^^ -----
@@ -98,6 +98,8 @@ jobs:
           #                   "py": the_py,
           #                   "arch": the_arch,
           #               }
+          #               if the_os == "macos":
+          #                   them["os-version"] = "13"
           #               print(f"- {json.dumps(them)}")
           # ]]]
           - {"os": "ubuntu", "py": "cp38", "arch": "x86_64"}
@@ -115,16 +117,16 @@ jobs:
           - {"os": "ubuntu", "py": "cp310", "arch": "aarch64"}
           - {"os": "ubuntu", "py": "cp311", "arch": "aarch64"}
           - {"os": "ubuntu", "py": "cp312", "arch": "aarch64"}
-          - {"os": "macos", "py": "cp38", "arch": "arm64"}
-          - {"os": "macos", "py": "cp39", "arch": "arm64"}
-          - {"os": "macos", "py": "cp310", "arch": "arm64"}
-          - {"os": "macos", "py": "cp311", "arch": "arm64"}
-          - {"os": "macos", "py": "cp312", "arch": "arm64"}
-          - {"os": "macos", "py": "cp38", "arch": "x86_64"}
-          - {"os": "macos", "py": "cp39", "arch": "x86_64"}
-          - {"os": "macos", "py": "cp310", "arch": "x86_64"}
-          - {"os": "macos", "py": "cp311", "arch": "x86_64"}
-          - {"os": "macos", "py": "cp312", "arch": "x86_64"}
+          - {"os": "macos", "py": "cp38", "arch": "arm64", "os-version": "13"}
+          - {"os": "macos", "py": "cp39", "arch": "arm64", "os-version": "13"}
+          - {"os": "macos", "py": "cp310", "arch": "arm64", "os-version": "13"}
+          - {"os": "macos", "py": "cp311", "arch": "arm64", "os-version": "13"}
+          - {"os": "macos", "py": "cp312", "arch": "arm64", "os-version": "13"}
+          - {"os": "macos", "py": "cp38", "arch": "x86_64", "os-version": "13"}
+          - {"os": "macos", "py": "cp39", "arch": "x86_64", "os-version": "13"}
+          - {"os": "macos", "py": "cp310", "arch": "x86_64", "os-version": "13"}
+          - {"os": "macos", "py": "cp311", "arch": "x86_64", "os-version": "13"}
+          - {"os": "macos", "py": "cp312", "arch": "x86_64", "os-version": "13"}
           - {"os": "windows", "py": "cp38", "arch": "x86"}
           - {"os": "windows", "py": "cp39", "arch": "x86"}
           - {"os": "windows", "py": "cp310", "arch": "x86"}
@@ -135,7 +137,7 @@ jobs:
           - {"os": "windows", "py": "cp310", "arch": "AMD64"}
           - {"os": "windows", "py": "cp311", "arch": "AMD64"}
           - {"os": "windows", "py": "cp312", "arch": "AMD64"}
-        # [[[end]]] (checksum: a6ca53e9c620c9e5ca85e7322122056c)
+        # [[[end]]] (checksum: 16ed28c185d540b2d9972a0217864472)
       fail-fast: false
 
     steps:
diff --git a/.github/workflows/quality.yml b/.github/workflows/quality.yml
index 3376aafd1..c9718bf11 100644
--- a/.github/workflows/quality.yml
+++ b/.github/workflows/quality.yml
@@ -31,7 +31,9 @@ jobs:
     # Because pylint can report different things on different OS's (!)
     # (https://github.com/PyCQA/pylint/issues/3489), run this on Mac where local
     # pylint gets run.
-    runs-on: macos-latest
+    # GitHub is rolling out macos 14, but it doesn't have Python 3.8 or 3.9.
+    # https://mastodon.social/@hugovk/112320493602782374
+    runs-on: macos-13
 
     steps:
       - name: "Check out the repo"
diff --git a/.github/workflows/testsuite.yml b/.github/workflows/testsuite.yml
index e6742753e..e11b3d74e 100644
--- a/.github/workflows/testsuite.yml
+++ b/.github/workflows/testsuite.yml
@@ -30,7 +30,7 @@ concurrency:
 jobs:
   tests:
     name: "${{ matrix.python-version }} on ${{ matrix.os }}"
-    runs-on: "${{ matrix.os }}-latest"
+    runs-on: "${{ matrix.os }}-${{ matrix.os-version || 'latest' }}"
     # Don't run tests if the branch name includes "-notests"
     if: "!contains(github.ref, '-notests')"
     strategy:
@@ -62,6 +62,16 @@ jobs:
             python-version: "pypy-3.9"
           - os: windows
             python-version: "pypy-3.10"
+        # GitHub is rolling out macos 14, but it doesn't have Python 3.8 or 3.9.
+        # https://mastodon.social/@hugovk/112320493602782374
+        include:
+          - python-version: "3.8"
+            os: "macos"
+            os-version: "13"
+          - python-version: "3.9"
+            os: "macos"
+            os-version: "13"
+
       fail-fast: false
 
     steps: