diff --git a/docs/requirements.txt b/docs/requirements.txt
index e30e7a8..7938612 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,3 +1,3 @@
-sphinx
+sphinx==4.3.1
 sphinx-rtd-theme
 sphinx-rtd-dark-mode
\ No newline at end of file