diff --git a/.github/workflows/test-build-optional.yml b/.github/workflows/test-build-optional.yml
index 5c385d65..9ecdf8c5 100644
--- a/.github/workflows/test-build-optional.yml
+++ b/.github/workflows/test-build-optional.yml
@@ -11,8 +11,8 @@ jobs:
       fail-fast: false
       matrix:
         os:
-          - ubuntu
-          - macos
+          - ubuntu-latest
+          - macos-13
         python-version:
           - pypy-3.6
           - pypy-3.7
@@ -28,7 +28,7 @@ jobs:
         exclude:
           - {os: "macos",  python-version: "pypy-3.6"}
           - {os: "macos",  python-version: "pypy-3.9"}
-    runs-on: ${{ matrix.os }}-latest
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Check out repository code
         uses: actions/checkout@v4
diff --git a/.github/workflows/test-unit-optional.yml b/.github/workflows/test-unit-optional.yml
index 4e481af6..7254a07b 100644
--- a/.github/workflows/test-unit-optional.yml
+++ b/.github/workflows/test-unit-optional.yml
@@ -11,8 +11,8 @@ jobs:
       fail-fast: false
       matrix:
         os:
-          - ubuntu
-          - macos
+          - ubuntu-latest
+          - macos-13
         python-version:
           - pypy-3.6
           - pypy-3.7
@@ -27,7 +27,7 @@ jobs:
         exclude:
           - {os: "macos",  python-version: "pypy-3.6"}
           - {os: "macos",  python-version: "pypy-3.9"}
-    runs-on: ${{ matrix.os }}-latest
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Check out repository code
         uses: actions/checkout@v4