diff --git a/test-requirements.txt b/test-requirements.txt
index 2b99ae8882..6e3986139e 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -4,7 +4,7 @@
 # Hacking already pins down pep8, pyflakes and flake8
 hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
 bandit>=1.1.0 # Apache-2.0
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 os-api-ref>=1.4.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0