diff --git a/test-requirements.txt b/test-requirements.txt
index 7207d88..242d3dc 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -6,7 +6,7 @@
 
 coverage!=4.4,>=4.0 # Apache-2.0
 python-subunit>=1.0.0 # Apache-2.0/BSD
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 oslosphinx>=4.7.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD