diff --git a/doc/requirements.txt b/doc/requirements.txt
index a3a98ff..4d5891e 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,2 +1,3 @@
-sphinx!=1.6.6,!=1.6.7,>=1.6.5 # BSD
+sphinx>=1.8.0,<2.0.0;python_version=='2.7' # BSD
+sphinx>=1.8.0;python_version>='3.4'  # BSD
 openstackdocstheme>=1.19.0 # Apache-2.0