diff --git a/tox.ini b/tox.ini
index 460207f..f9ef0c1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,7 +9,7 @@ recreate = true
 commands =
     py.test {posargs}
 deps:
-    tornado
+    tornado<6
     coverage>=4.0
     pytest-isort
     pytest-cache>=1.0