diff --git a/doc/requirements.txt b/doc/requirements.txt
index 63659fbc3..563a1e35b 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -5,6 +5,6 @@
 openstackdocstheme>=1.11.0  # Apache-2.0
 reno>=0.1.1  # Apache2
 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
 sphinxcontrib-httpdomain
 sphinxcontrib-pecanwsme>=0.8