diff --git a/.github/workflows/manual_tests.yml b/.github/workflows/manual_tests.yml
index 63c8f93..2781c64 100644
--- a/.github/workflows/manual_tests.yml
+++ b/.github/workflows/manual_tests.yml
@@ -65,7 +65,9 @@ jobs:
       - name: Install pdm
         run: pip install pdm
       - name: Generate lock with oldest dependencies
-        run: pdm lock --lockfile pdm.oldest.lock --strategy no_cross_platform,direct_minimal_versions -G cli -dG test
+        run: |
+          pdm add "fiona<1.10"
+          pdm lock --lockfile pdm.oldest.lock --strategy no_cross_platform,direct_minimal_versions -G cli -dG test
       - name: Install quackosm and tests dependencies
         run: pdm install --lockfile pdm.oldest.lock -G cli -dG test --skip=post_install
       - name: Run tests with pytest