diff --git a/setup.py b/setup.py
index 09e10111..65fd3b5c 100644
--- a/setup.py
+++ b/setup.py
@@ -43,6 +43,7 @@ def setup_package():
             "pytz>=2020.1",
             'typing_extensions;python_version<"3.11"',
             "python-dateutil>=2.8.1,<3",
+            "sortedcontainers>=2"
         ],
         extras_require={
             "test": [