diff --git a/requirements.txt b/requirements.txt
index ebb23c3..b877312 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,16 +12,16 @@
 python-ceilometerclient>=1.0.6
 python-glanceclient>=0.15.0
 python-keystoneclient>=1.1.0
-python-novaclient>=2.18.0
-python-neutronclient>=2.3.6,<3
+python-novaclient>=2.18.0,!=2.21.0
+python-neutronclient>=2.3.11,<3
 python-cinderclient>=1.1.0
-python-heatclient>=0.2.9
+python-heatclient>=0.3.0
 python-ironicclient>=0.2.1
 python-saharaclient>=0.7.6
 python-swiftclient>=2.2.0
 testrepository>=0.0.18
 oslo.config>=1.6.0  # Apache-2.0
-six>=1.7.0
+six>=1.9.0
 iso8601>=0.1.9
 fixtures>=0.3.14
 testscenarios>=0.4