diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b4019757..fef731f2 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -70,6 +70,10 @@ jobs:
       HYPOTHESIS_PROFILE: 'ci'
       # Activate Python development mode so we get warnings.
       PYTHONDEVMODE: '1'
+      # Make uv use the Python installed by setup-python. uv only uses a
+      # free-threaded interpreter when explicitly requested, and would otherwise
+      # silently fall back to a GIL-enabled Python found on the system.
+      UV_PYTHON: ${{ matrix.py }}
     steps:
       - name: Set up Python
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
diff --git a/.github/workflows/typing.yml b/.github/workflows/typing.yml
index 35786201..1555a8ee 100644
--- a/.github/workflows/typing.yml
+++ b/.github/workflows/typing.yml
@@ -23,7 +23,17 @@ jobs:
           - '3.14'
           - '3.14t'
     runs-on: 'ubuntu-24.04'
+    env:
+      # Make uv use the Python installed by setup-python instead of the
+      # system Python.
+      UV_PYTHON: ${{ matrix.py }}
     steps:
+      - name: Set up Python
+        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        with:
+          python-version: ${{ matrix.py }}
+          allow-prereleases: true
+
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false