diff --git a/setup.py b/setup.py
index 12f3337..fc30024 100644
--- a/setup.py
+++ b/setup.py
@@ -269,6 +269,7 @@ def get_simple_vars_from_src(src):
     extras_require={
         ':python_version == "2.7"': [
             'futures>=1.0',
+            'enum34>=1.1'
         ],
     },
     install_requires=required,
diff --git a/tox.ini b/tox.ini
index dd4f1fb..ccb442d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -135,3 +135,11 @@ commands = python setup.py build_sphinx
 [testenv:bandit]
 deps = bandit
 commands = bandit -r exec_helpers
+
+[testenv:dep-graph]
+envdir = {toxworkdir}/dep-graph
+deps =
+    pipenv
+commands =
+    pipenv install -r {toxinidir}/build_requirements.txt --skip-lock
+    pipenv graph