diff --git a/docs/requirements.txt b/docs/requirements.txt
index 773b92cea..a99d1b78f 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,4 +1,4 @@
-Sphinx>=2.1
-sphinx-hoverxref
-sphinx-notfound-page
-sphinx_rtd_theme
+Sphinx==3.0.1
+sphinx-hoverxref==0.2b1
+sphinx-notfound-page==0.4
+sphinx_rtd_theme==0.4.3