diff --git a/doc/requirements.txt b/doc/requirements.txt
index f1fb97c..6734c53 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,4 +1,5 @@
-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
 openstackdocstheme>=1.18.1 # Apache-2.0