diff --git a/test-requirements.txt b/test-requirements.txt
index b8b5809..98f7928 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -12,6 +12,6 @@ testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT
 oslotest>=3.2.0 # Apache-2.0
 os-testr>=1.0.0 # Apache-2.0
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 oslosphinx>=4.7.0 # Apache-2.0
 mock>=2.0.0 # BSD