diff --git a/pyproject.toml b/pyproject.toml
index f79589293..dfe8ca63b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,6 +42,7 @@ Documentation = 'https://aiida-quantumespresso.readthedocs.io'
 docs = [
     'Sphinx',
     'docutils',
+    'markupsafe<2.1',
     'sphinx-copybutton~=0.3.0',
     'sphinx-book-theme~=0.1.0',
     'sphinx-click~=2.7.1'