diff --git a/changelog/440.bugfix.rst b/changelog/440.bugfix.rst
new file mode 100644
index 00000000..49ce5d4f
--- /dev/null
+++ b/changelog/440.bugfix.rst
@@ -0,0 +1 @@
+Fix mark argument parsing in the new pytest hook.
diff --git a/dkist/conftest.py b/dkist/conftest.py
index 12986337..0f8b7c9b 100644
--- a/dkist/conftest.py
+++ b/dkist/conftest.py
@@ -362,6 +362,6 @@ def pytest_runtest_call(item):
         if ds:
             item.funcargs[replace_arg] = load_dataset(ds)
         if tds:
-            item.funcargs[tdsmark.args[0]] = load_dataset(tds)
+            item.funcargs[replace_arg] = load_dataset(tds)
 
     yield item