diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 7c85de3..844c3ae 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -14,7 +14,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "3.13t", "3.14-dev", "3.14t-dev"]
         os: [windows-latest, ubuntu-latest, macos-latest]
 
     env:
@@ -37,7 +37,7 @@ jobs:
           __version__\s*=\s*(?:['"])([[:PEP440:]])(?:['"])
 
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@f677139bbe7f9c59b41e40162b753c062f5d49a3  # v5.2.0
+      uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c  # v6.0.0
       if: steps.release.outputs.version == 0
       with:
         python-version: ${{ matrix.python-version }}
@@ -46,5 +46,11 @@ jobs:
       if: steps.release.outputs.version == 0
       run: |
         python -m pip install -U pip setuptools wheel
-        python -m pip install -e .[test]
+        python -m pip install .[test] --use-pep517
         python -m unittest -v tests.suite
+
+    - name: Test (free-threading stress test)
+      if: ${{ (steps.release.outputs.version == 0) && endsWith(matrix.python-version, 't') }}
+      run: |
+        python -m pip install unittest-ft
+        unittest-ft -s -v