diff --git a/requirements.txt b/requirements.txt
index 1f6436a5..7dcd4334 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,6 +7,6 @@ iso8601>=0.1.11 # MIT
 lxml!=3.7.0,>=3.4.1 # BSD
 oslo.config>=5.1.0 # Apache-2.0
 docutils>=0.11 # OSI-Approved Open Source, Public Domain
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 demjson>=2.2.2 # GLGPLv3+
 PyYAML>=3.10 # MIT