diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index ee59ab67..e35a948c 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -26,6 +26,13 @@ jobs:
         - "3.15"
         - "3.15t"
         os: [ubuntu-latest, macos-latest]
+        exclude:
+        # ubuntu-latest is Ubuntu 26.04, which has no Python 3.9 in setup-python.
+        - python-version: "3.9"
+          os: ubuntu-latest
+        include:
+        - python-version: "3.9"
+          os: ubuntu-24.04
 
     env:
       PIP_DISABLE_PIP_VERSION_CHECK: 1