diff --git a/requirements.txt b/requirements.txt
index 92cfbcf892a..7c4280e17c3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,7 +5,7 @@ jupyter==1.0.0
 
 coverage==4.1
 nose==1.3.7
-tornado
+tornado==4.5.3
 flake8==2.5.2
 tqdm
 networkx==2.1