diff --git a/requirements.txt b/requirements.txt
index 5f66ab60a..4f951d9d3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@ oslo.config>=1.2.0
 stevedore>=0.10
 
 # for timeutils
-iso8601>=0.1.4,!=0.1.5,!=0.1.6,!=0.1.7
+iso8601>=0.1.8
 
 # for jsonutils
 six>=1.4.1