diff --git a/pyproject.toml b/pyproject.toml
index 2113e39..26c56df 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,6 +35,7 @@ Issues = "https://github.com/crate-py/rpds/issues/"
 Funding = "https://github.com/sponsors/Julian"
 Tidelift = "https://tidelift.com/subscription/pkg/pypi-rpds-py?utm_source=pypi-rpds-py&utm_medium=referral&utm_campaign=pypi-link"
 Source = "https://github.com/crate-py/rpds"
+Upstream = "https://github.com/orium/rpds"
 
 [tool.black]
 line-length = 79