diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c2684d5fc..d68c4faa2 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -35,6 +35,7 @@ jobs:
             pip install https://github.com/3-manifolds/snappy_manifolds/archive/master.zip &&
             pip install https://github.com/3-manifolds/Spherogram/archive/master.zip
           CIBW_BEFORE_TEST: >
+            pip install cython &&
             pip install https://github.com/3-manifolds/PLink/archive/master.zip &&
             pip install https://github.com/3-manifolds/snappy_manifolds/archive/master.zip &&
             pip install git+https://github.com/3-manifolds/Spherogram