diff --git a/.isort.cfg b/.isort.cfg
index cca9d19..56b0448 100644
--- a/.isort.cfg
+++ b/.isort.cfg
@@ -3,6 +3,7 @@ not_skip = __init__.py
 skip = workbench.py
 known_third_party =
     dateutil,
+    medallion,
     ordereddict,
     pytest,
     pytz,
diff --git a/tox.ini b/tox.ini
index 7c2e68c..683e137 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,7 @@ deps =
   pytest-cov
   coverage
   taxii2-client
+  medallion
 commands =
   pytest --ignore=stix2/test/test_workbench.py --cov=stix2 stix2/test/ --cov-report term-missing
   pytest stix2/test/test_workbench.py --cov=stix2 --cov-report term-missing --cov-append