diff --git a/.github/workflows/gmy-tool.yml b/.github/workflows/gmy-tool.yml
index affaa46d5..d85418aed 100644
--- a/.github/workflows/gmy-tool.yml
+++ b/.github/workflows/gmy-tool.yml
@@ -119,7 +119,7 @@ jobs:
 
       - name: Install test dependencies
         working-directory: python-tools
-        run: pip install pytest cython && python setup.py install
+        run: pip install pytest 'cython~=0.29' && python setup.py install
 
       - name: Run the tests
         working-directory: geometry-tool/tests
diff --git a/python-tools/pyproject.toml b/python-tools/pyproject.toml
index b4d35b402..49e593b37 100644
--- a/python-tools/pyproject.toml
+++ b/python-tools/pyproject.toml
@@ -1,3 +1,3 @@
 [build-system]
-requires = ["setuptools", "wheel", "Cython", "numpy"]
+requires = ["setuptools", "wheel", "Cython ~= 0.29", "numpy"]
 build-backend = "setuptools.build_meta"