diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ea2f40c45968ed52baff0153146e607fa7781a05..4a348663760ddd1c9decf9e3b9a95dbb78b09664 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -4,4 +4,5 @@ build:
     - docker
   script:
     - pip install --upgrade pip setuptools wheel
+    - pip install cython
     - pip install '.'