diff --git a/requirements/docs.txt b/requirements/docs.txt
index 7444287ed4..b5056fc2da 100644
--- a/requirements/docs.txt
+++ b/requirements/docs.txt
@@ -1,4 +1,4 @@
-sphinx>=3.0, !=3.5  # fails with sphinx.ext.viewcode
+sphinx>=3.0, <3.5  # fails with sphinx.ext.viewcode  # fails with sphinx_paramlinks with 4.0.0
 recommonmark  # fails with badges
 m2r  # fails with multi-line text
 nbsphinx>=0.8