diff --git a/user_guide_src/requirements.txt b/user_guide_src/requirements.txt
index 19f5064b98..5d11554964 100644
--- a/user_guide_src/requirements.txt
+++ b/user_guide_src/requirements.txt
@@ -2,3 +2,4 @@ sphinx>=2.4.4,<3
 sphinxcontrib-phpdomain>=0.7.1
 docutils>=0.16
 sphinx-rtd-theme>=0.5.0
+jinja2<3.1