diff --git a/constraints.txt b/constraints.txt
index 10af17e04..71c6a7856 100644
--- a/constraints.txt
+++ b/constraints.txt
@@ -200,7 +200,7 @@ sphinxcontrib-jsmath==1.0.1
     # via sphinx
 sphinxcontrib-qthelp==1.0.3
     # via sphinx
-sphinxcontrib-serializinghtml==1.1.5
+sphinxcontrib-serializinghtml==1.1.9
     # via sphinx
 sspilib==0.1.0
     # via pyspnego