diff --git a/setup.py b/setup.py
index 4d1fa0b5..abc4b4b4 100644
--- a/setup.py
+++ b/setup.py
@@ -164,7 +164,7 @@ setup(name = 'GPy',
       py_modules = ['GPy.__init__'],
       test_suite = 'GPy.testing',
       setup_requires = ['numpy>=1.7'],
-      install_requires = ['numpy>=1.7', 'scipy>=1.3.0', 'six', 'paramz>=0.9.0'],
+      install_requires = ['numpy>=1.7', 'scipy>=1.3.0', 'six', 'paramz>=0.9.0', 'cython>=0.29'],
       extras_require = {'docs':['sphinx'],
                         'optional':['mpi4py',
                                     'ipython>=4.0.0',