diff --git a/requirements/devel.txt b/requirements/devel.txt
index 23d99790..25c7fb84 100644
--- a/requirements/devel.txt
+++ b/requirements/devel.txt
@@ -18,6 +18,7 @@ pytest-timeout
 sphinx==2.2.0 ; python_version >= '3.0'
 sphinx==1.8.5 ; python_version < '3.0'
 Jinja2==2.10
+markupsafe==1.1.1
 doc2dash==2.3.0
 beautifulsoup4
 attrdict3