diff --git a/requirements.txt b/requirements.txt
index dc47abe8..5114a8b2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,9 +1,9 @@
 # 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
 
-Babel>=2.3.4 # BSD
+Babel!=2.4.0,>=2.3.4 # BSD
 six>=1.9.0 # MIT
 keystoneauth1>=2.18.0 # Apache-2.0
 stevedore>=1.20.0 # Apache-2.0