diff --git a/tox.ini b/tox.ini
index f938545..df0d8f3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,6 +19,7 @@ setenv =
   coverage: COVERAGE={env:COVERAGE_CONFIG}
 deps =
   -rtest-requirements.txt
+  factur-x==1.8
 commands =
   py.test {env:COVERAGE:} {env:JUNIT:} {posargs}