diff --git a/requirements_dev.txt b/requirements_dev.txt
index c7984aa..4900852 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -19,6 +19,6 @@ pytest-runner==2.11.1
 tox==2.7.0
 flake8==3.4.1
 coverage==4.4.1
-Sphinx==1.6.3
+Sphinx==4.0.1
 sphinxcontrib-napoleon==0.6.1
 cryptography==2.6.1