diff --git a/tests/extensions/test_custom.py b/tests/extensions/test_custom.py
index 1bd723471..48e4ef3f5 100644
--- a/tests/extensions/test_custom.py
+++ b/tests/extensions/test_custom.py
@@ -48,7 +48,7 @@ def add_link(self, target: pystac.STACObject) -> None:
 
     @classmethod
     def get_schema_uri(cls) -> str:
-        return super().get_schema_uri()
+        raise NotImplementedError
 
     @staticmethod
     def custom_ext(obj: T) -> "CustomExtension[T]":