diff --git a/doc/requirements.txt b/doc/requirements.txt
index 31f2b4c7e5..5864616975 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,6 +1,8 @@
 # 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.
-sphinx>=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
 sphinxcontrib-blockdiag>=1.1.0
 openstackdocstheme>=1.28.0 # Apache-2.0
diff --git a/doc/source/install/plugins/deploy-tap-as-a-service-neutron-plugin.rst b/doc/source/install/plugins/deploy-tap-as-a-service-neutron-plugin.rst
index 50b6ececd1..bd462f395e 100644
--- a/doc/source/install/plugins/deploy-tap-as-a-service-neutron-plugin.rst
+++ b/doc/source/install/plugins/deploy-tap-as-a-service-neutron-plugin.rst
@@ -250,7 +250,7 @@ Neutron and Horizon LOCI images
 
 
 Deploy TaaS Plugin
-====================
+==================
 
 Override images in Neutron chart
 ---------------------------------
@@ -299,7 +299,7 @@ to configure the ``service_provider`` endpoint used by Neutron TaaS plugin:
 
 
 Deploy TaaS Dashboard Plugin
-==============================
+============================
 
 TaaS dashboard plugin can be deployed simply by using custom LOCI images having
 TaaS Dashboard code installed (as explained in above sections), i.e. override
@@ -314,7 +314,7 @@ the :code:`images` section parameters for Horizon charts:
 
 
 Set log level for TaaS
-=======================
+======================
 
 Default log level for Neutron TaaS is :code:`INFO`. For changing it, override
 following parameter:
diff --git a/doc/source/testing/ceph-resiliency/host-failure.rst b/doc/source/testing/ceph-resiliency/host-failure.rst
index 344078fc49..002c67a0aa 100644
--- a/doc/source/testing/ceph-resiliency/host-failure.rst
+++ b/doc/source/testing/ceph-resiliency/host-failure.rst
@@ -98,7 +98,7 @@ Ceph status shows that the monitor running on ``voyager3`` is now in quorum.
       pgs:     182 active+clean
 
 Case: A host machine where ceph-mon is running is down
-========================================================
+======================================================
 
 This is for the case when a host machine (where ceph-mon is running) is down.