diff --git a/tox.ini b/tox.ini
index 2719c137a..bc44df987 100644
--- a/tox.ini
+++ b/tox.ini
@@ -203,6 +203,7 @@ commands =
 [testenv:sphinx]
 basepython = {env:PYTHON:python3}
 passenv =
+usedevelop = true
 deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/misc/requirements/requirements-pyqt.txt