diff --git a/doc/requirements.txt b/doc/requirements.txt
index 4ddc914d83..6adf3a64ec 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -2,7 +2,8 @@ mock>=2.0.0 # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
 os-api-ref>=1.4.0 # 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
 sphinxcontrib-pecanwsme>=0.10.0 # Apache-2.0
 sphinxcontrib-seqdiag>=0.8.4 # BSD