diff --git a/requirements.txt b/requirements.txt
index ab48ec5..b15fb92 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -19,3 +19,6 @@
 testrepository>=0.0.17
 oslo.config>=1.1.0
 eventlet>=0.13.0
+six<1.4.0
+iso8601>=0.1.4
+fixtures>=0.3.14