diff --git a/doc/sphinx/requirements.txt b/doc/sphinx/requirements.txt
index 5e99b375e7..eab1576220 100644
--- a/doc/sphinx/requirements.txt
+++ b/doc/sphinx/requirements.txt
@@ -1,3 +1,4 @@
-sphinx_rtd_theme
+Sphinx==3.5.4
+sphinx_rtd_theme==1.1.1
 lxml