diff --git a/tests/README.md b/tests/README.md
index 354d644..a6bdb62 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -50,3 +50,10 @@ please send a PR.
 If you think the disagreement is due to a genuine error or oversight in the
 KDL specification, please open an issue explaining the matter and the change
 will be considered for the next version of the KDL spec.
+
+## Credit
+
+This test suite was extracted from
+[`kdl4j`](https://github.com/hkolbeck/kdl4j), the original Java
+implementation of KDL, with huge thanks to
+[@hkolbeck](https://github.com/hkolbeck) for authoring them!