diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 00ae46e..089d167 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -17,8 +17,11 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         python-version: ["3.9"]
-        pyyaml-version: ["3.13", "4.2b4", "5.4", "6.0"]
+        pyyaml-version: ["4.2b4", "5.4", "6.0"]
         include:
+          - { os: ubuntu-latest, python-version: "3.7", pyyaml-version: "3.13" }
+          - { os: macos-latest, python-version: "3.7", pyyaml-version: "3.13" }
+          - { os: windows-latest, python-version: "3.7", pyyaml-version: "3.13" }
           - { os: ubuntu-latest, python-version: "3.13", pyyaml-version: "6.0" }
           - { os: macos-latest, python-version: "3.13", pyyaml-version: "6.0" }
           - { os: windows-latest, python-version: "3.13", pyyaml-version: "6.0" }