diff --git a/test-requirements.txt b/test-requirements.txt
index 8c1d78735a..e0d270c7e3 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -8,7 +8,7 @@ fixtures>=3.0.0 # Apache-2.0/BSD
 flake8-import-order==0.12 # LGPLv3
 mock>=2.0.0 # BSD
 
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,>=1.6.2 # BSD
 psycopg2>=2.6.2 # LGPL/ZPL
 PyMySQL>=0.7.6 # MIT License
 oslosphinx>=4.7.0 # Apache-2.0