diff --git a/requirements.txt b/requirements.txt
index e337026..4f71e96 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,6 +5,6 @@
 pbr>=2.0.0  # Apache-2.0
 
 oslosphinx>=4.7.0 # Apache-2.0
-sphinx>=1.5.1 # BSD
+sphinx>=1.5.1,<1.6 # BSD
 
 yasfb>=0.5.1