diff --git a/test-requirements.txt b/test-requirements.txt
index e446fe8..14999ca 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -14,6 +14,6 @@ testtools>=2.2.0 # MIT
 
 # documentation
 doc8>=0.6.0 # Apache-2.0
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 reno>=2.5.0 # Apache-2.0
 openstackdocstheme>=1.17.0 # Apache-2.0