diff --git a/doc/utils/requirements.txt b/doc/utils/requirements.txt
index 9b8e106875..900ca8a162 100644
--- a/doc/utils/requirements.txt
+++ b/doc/utils/requirements.txt
@@ -1,7 +1,7 @@
-Sphinx
-sphinxcontrib-spelling
+Sphinx==4.2.0
+sphinxcontrib-spelling==7.2.1
 git+git://github.com/akohlmey/sphinx-fortran@parallel-read
-sphinx_tabs
-breathe
-Pygments
-six
+sphinx_tabs==3.2.0
+breathe==4.31.0
+Pygments==2.10.0
+six==1.16.0