diff --git a/requirements.txt b/requirements.txt
index 889438e8f44a2119fc04764ae9a642812055c844..270f82f988f5d487fea5e0254aa94e285e2aedc4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,6 @@
 # Add your requirements here like:
 six
+cython
 numpy>=1.4
 scipy>=0.9
 matplotlib