1 files changed, 3 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini

index 2b3d39e034..41678aa38b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -124,6 +124,9 @@ usedevelop = false
 deps =
     Automat == 0.8.0
     lxml
+    # markupsafe 2.1 introduced a change that breaks Jinja 2.x. Since we depend on
+    # Jinja >= 2.9, it means this test suite will fail if markupsafe >= 2.1 is installed.
+    markupsafe < 2.1
     {[base]deps}
 
 commands =