diff --git a/requirements.txt b/requirements.txt
index db647de59..aa43e7466 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-pbr>=2.0.0 # Apache-2.0
+pbr!=2.1.0,>=2.0.0 # Apache-2.0
 cliff>=2.3.0 # Apache-2.0
 debtcollector>=1.2.0 # Apache-2.0
 iso8601>=0.1.11 # MIT
@@ -18,4 +18,4 @@ python-keystoneclient>=3.8.0 # Apache-2.0
 requests!=2.12.2,!=2.13.0,>=2.10.0 # Apache-2.0
 simplejson>=2.2.0 # MIT
 six>=1.9.0 # MIT
-Babel>=2.3.4 # BSD
+Babel!=2.4.0,>=2.3.4 # BSD