diff --git a/doc/requirements.txt b/doc/requirements.txt
index 45d0110674..0a78486289 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -4,4 +4,5 @@
 doc8>=0.6.0 # Apache-2.0
 openstackdocstheme>=1.18.1 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-sphinx!=1.6.6,>=1.6.2 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
diff --git a/lower-constraints.txt b/lower-constraints.txt
index 6b47a50e93..4c7337c8f5 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -10,7 +10,7 @@ chardet==3.0.4
 cliff==2.11.0
 cmd2==0.8.1
 coverage==4.0
-cryptography==1.9
+cryptography==2.1.4
 ddt==1.0.1
 debtcollector==1.19.0
 decorator==4.2.1
diff --git a/requirements.txt b/requirements.txt
index f6e4031332..3c88d2d077 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,6 @@
 # process, which may cause wedges in the gate later.
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 docker>=2.4.2 # Apache-2.0
-cryptography>=1.9 # BSD/Apache-2.0
 Jinja2>=2.8 # BSD License (3 clause)
 GitPython>=1.0.1 # BSD License (3 clause)
 six>=1.10.0 # MIT