diff --git a/tox.ini b/tox.ini
index 8fcb7b177..b646fd285 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,6 +6,7 @@ deps=
     nose
     sqlalchemy
     whoosh
+    html5lib
 setenv =
     SPHINX_TEST_TEMPDIR = {envdir}/testbuild
 commands=