diff --git a/docs/requirements.txt b/docs/requirements.txt
index 4179eeb..fc516d5 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,7 +1,7 @@
-sphinx==4.2.0
-docutils==0.17.1
+sphinx==3.5.1
+docutils==0.16.0
 sphinx-prompt==1.1.0
-sphinx-tabs==3.2.0
+sphinx-tabs==2.0.1
 sphinx-rtd-theme==1.0.0
 sphinx-notfound-page==0.3
 sphinx-js==3.1