diff --git a/doc/utils/requirements.txt b/doc/utils/requirements.txt
index 9b8e106875..7e4563a1ec 100644
--- a/doc/utils/requirements.txt
+++ b/doc/utils/requirements.txt
@@ -1,4 +1,4 @@
-Sphinx
+Sphinx==4.0.3
 sphinxcontrib-spelling
 git+git://github.com/akohlmey/sphinx-fortran@parallel-read
 sphinx_tabs