diff --git a/tox.ini b/tox.ini
index 7afa4b0d0..abbae820a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -177,7 +177,7 @@ deps =
     pyflakes==1.2.3
     pyparsing==2.1.4
     six==1.10.0
-    sortedcontainers==1.4.4
+    sortedcontainers==1.5.1
     venusian==1.0
 commands =
     {envpython} -m flake8