diff --git a/test-requirements.txt b/test-requirements.txt
index b9734ef24d..e6bbc407ec 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -22,7 +22,7 @@ lxml!=3.7.0,>=2.3 # BSD
 mock>=2.0 # BSD
 oslotest>=1.10.0 # Apache-2.0
 # required to build documentation
-sphinx>=1.5.1 # BSD
+sphinx!=1.6.1,>=1.5.1 # BSD
 os-api-ref>=1.0.0 # Apache-2.0
 # test wsgi apps without starting an http server
 WebTest>=2.0 # MIT