diff --git a/addon/flamenco/bat/interface.py b/addon/flamenco/bat/interface.py
index e02fc022..d6333c7d 100644
--- a/addon/flamenco/bat/interface.py
+++ b/addon/flamenco/bat/interface.py
@@ -197,7 +197,7 @@ def copy(  # type: ignore
     *,
     relative_only: bool,
     packer_class=pack.Packer,
-    **packer_kwargs: dict[Any, Any],
+    packer_kwargs: Optional[dict[Any, Any]] = None,
 ) -> PackThread:
     """Use BAT to copy the given file and dependencies to the target location.
 
@@ -210,6 +210,8 @@ def copy(  # type: ignore
         if _running_packthread is not None:
             raise RuntimeError("other packing operation already in progress")
 
+    if packer_kwargs is None:
+        packer_kwargs = {}
     packer = packer_class(
         base_blendfile,
         project,
diff --git a/addon/flamenco/operators.py b/addon/flamenco/operators.py
index b6b21b24..c3cd7e50 100644
--- a/addon/flamenco/operators.py
+++ b/addon/flamenco/operators.py
@@ -301,9 +301,11 @@ class FLAMENCO_OT_submit_job(FlamencoOpMixin, bpy.types.Operator):
             target="/",  # Target directory irrelevant for Shaman transfers.
             exclusion_filter="",  # TODO: get from GUI.
             relative_only=True,  # TODO: get from GUI.
-            api_client=self.get_api_client(context),
-            checkout_path=checkout_root,
             packer_class=bat_shaman.Packer,
+            packer_kwargs=dict(
+                api_client=self.get_api_client(context),
+                checkout_path=checkout_root,
+            ),
         )
 
         return checkout_root / blendfile.name  # TODO: get relative to the checkout dir.