diff --git a/requirements.txt b/requirements.txt
index f68438afea..fe7bc08861 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 pbr>=0.6,!=0.7,<1.0
-six>=1.7.0
+six>=1.9.0
 
 Babel>=1.3
 cliff>=1.7.0  # Apache-2.0
@@ -12,9 +12,9 @@ oslo.i18n>=1.3.0  # Apache-2.0
 oslo.utils>=1.2.0                       # Apache-2.0
 oslo.serialization>=1.2.0               # Apache-2.0
 python-glanceclient>=0.15.0
-python-keystoneclient>=1.0.0
-python-novaclient>=2.18.0
+python-keystoneclient>=1.1.0
+python-novaclient>=2.18.0,!=2.21.0
 python-cinderclient>=1.1.0
-python-neutronclient>=2.3.6,<3
+python-neutronclient>=2.3.11,<3
 requests>=2.2.0,!=2.4.0
 stevedore>=1.1.0  # Apache-2.0