diff --git a/requirements.txt b/requirements.txt
index 80beaf1a..28c6d8d5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@
 # process, which may cause wedges in the gate later.
 pbr>=1.6 # Apache-2.0
 cliff!=1.16.0,!=1.17.0,>=1.15.0 # Apache-2.0
-iso8601>=0.1.9 # MIT
+iso8601>=0.1.11 # MIT
 netaddr!=0.7.16,>=0.7.12 # BSD
 requests!=2.9.0,>=2.8.1 # Apache-2.0
 python-keystoneclient!=1.8.0,!=2.1.0,>=1.6.0 # Apache-2.0