diff --git a/requirements.txt b/requirements.txt
index 2115be1..bbbdbf6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,3 +10,4 @@ Pygments==2.0.2
 pyzmq==14.7.0
 terminado==0.5
 tornado==4.2
+enum34==1.0.4