diff --git a/setup.cfg b/setup.cfg
index c565d81e..3463fec8 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -41,6 +41,7 @@ install_requires =
     requests>=2.22,<3
     SQLAlchemy-Continuum>=1.3.9,<2
     SQLAlchemy>=1.3.0,<1.4  # New 1.4 changes API, see #728
+    python-dateutil
 
 [options.extras_require]
 dev =