diff --git a/doc/requirements.txt b/doc/requirements.txt
index 44cc213fe..f556feaeb 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -5,4 +5,4 @@
 openstackdocstheme>=1.19.0 # Apache-2.0
 reno!=2.3.1,>=1.8.0 # Apache-2.0
 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
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2;python_version>='3.4'  # BSD