diff --git a/requirements.txt b/requirements.txt
index 8fe6a5ef1..1d1646657 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,7 @@
 wheel
 numpy
 numpy-financial
+cython
 Flask
 Werkzeug==2.0.3
 Flask-Login<0.3