diff --git a/src/setup.py b/src/setup.py
index 2904e7506..3815c4c53 100644
--- a/src/setup.py
+++ b/src/setup.py
@@ -196,7 +196,8 @@ setup(
         'kombu==4.6.*',
         'libsass==0.20.*',
         'lxml',
-        'markdown==3.3.*',
+        'markdown==3.3.4',  # 3.3.5 requires importlib-metadata>=4.4, but django-bootstrap3 requires importlib-metadata<3.
+        # We can upgrade markdown again once django-bootstrap3 upgrades or once we drop Python 3.6 and 3.7
         'mt-940==3.2',
         'oauthlib==3.1.*',
         'openpyxl==3.0.*',