diff --git a/setup.cfg b/setup.cfg
index 587a86c..9ccdf35 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -32,6 +32,7 @@ install_requires =
     jsonschema[format]
     pydantic[email] ~= 2.4
     requests
+    typing_extensions; python_version < "3.9"
     zarr_checksum
 zip_safe = False
 packages = find_namespace: