diff --git a/tox.ini b/tox.ini
index 5a232cd9..1fedc922 100644
--- a/tox.ini
+++ b/tox.ini
@@ -32,7 +32,7 @@ commands = mypy
 
 [testenv:docs]
 deps = -r requirements/docs.txt
-commands = sphinx-build -W -b dirhtml docs docs/_build/dirhtml
+commands = sphinx-build -E -W -b dirhtml docs docs/_build/dirhtml
 
 [testenv:update-requirements]
 deps =