diff --git a/doc/requirements.txt b/doc/requirements.txt
index 4faabc1b..a8778bf1 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -3,5 +3,6 @@
 # process, which may cause wedges in the gate later.
 openstackdocstheme>=1.18.1 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-sphinx!=1.6.6,!=1.6.7,>=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-apidoc>=0.2.0  # BSD