diff --git a/test-requirements.txt b/test-requirements.txt
index 729a25b126..d7a4d588e2 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -14,7 +14,7 @@ coverage!=4.4,>=4.0 # Apache-2.0
 ddt>=1.0.1 # MIT
 fixtures>=3.0.0 # Apache-2.0/BSD
 mock>=2.0.0 # BSD
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 requests>=2.14.2 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD
 testresources>=2.0.0 # Apache-2.0/BSD