diff --git a/tox.ini b/tox.ini
index 5a25381c62e2..d9c390dbd633 100644
--- a/tox.ini
+++ b/tox.ini
@@ -61,6 +61,7 @@ commands =
     python {toxinidir}/scripts/verify_included_modules.py
 deps =
     Sphinx
+    sphinx_rtd_theme
 passenv = {[testenv:system-tests]passenv} SPHINX_RELEASE READTHEDOCS LOCAL_RTD
 
 [testenv:docs-rtd]