diff --git a/setup.py b/setup.py
index 04f449bc..ea773bf4 100644
--- a/setup.py
+++ b/setup.py
@@ -33,6 +33,7 @@
         "cartopy",
         "chex",
         "colabtools",
+        "Cython",
         "dask",
         "dm-haiku",
         "jax",