diff --git a/doc-source/requirements.txt b/doc-source/requirements.txt
index e87c7e1..7020a9e 100644
--- a/doc-source/requirements.txt
+++ b/doc-source/requirements.txt
@@ -4,7 +4,7 @@ default-values>=0.4.2
 extras-require>=0.2.0
 furo>=2020.11.19b18
 seed-intersphinx-mapping>=0.3.1
-sphinx<3.4.0,>=3.0.3
+sphinx>=3.0.3,<3.6.0
 sphinx-copybutton>=0.2.12
 sphinx-notfound-page>=0.5
 sphinx-prompt>=1.1.0