diff --git a/src/anemoi/inference/checkpoint.py b/src/anemoi/inference/checkpoint.py
index 3bfe70b..80f75da 100644
--- a/src/anemoi/inference/checkpoint.py
+++ b/src/anemoi/inference/checkpoint.py
@@ -77,6 +77,10 @@ def typed_variables(self):
     def diagnostic_variables(self):
         return self._metadata.diagnostic_variables
 
+    @property
+    def prognostic_variables(self):
+        return self._metadata.prognostic_variables
+
     @property
     def prognostic_output_mask(self):
         return self._metadata.prognostic_output_mask
diff --git a/src/anemoi/inference/metadata.py b/src/anemoi/inference/metadata.py
index 838bcbb..f521825 100644
--- a/src/anemoi/inference/metadata.py
+++ b/src/anemoi/inference/metadata.py
@@ -36,6 +36,10 @@ def _remove_full_paths(x):
 
 
 class frozendict(dict):
+    def __deepcopy__(self, memo):
+        # As this is a frozendict, we can return the same object
+        return self
+
     def __setitem__(self, key, value):
         raise TypeError("frozendict is immutable")
 
diff --git a/src/anemoi/inference/runner.py b/src/anemoi/inference/runner.py
index 2856763..e8a74b0 100644
--- a/src/anemoi/inference/runner.py
+++ b/src/anemoi/inference/runner.py
@@ -55,7 +55,7 @@ def __init__(
         checkpoint,
         *,
         accumulations=True,
-        device: str,
+        device: str = "cuda",
         precision: str = None,
         report_error=False,
         allow_nans=None,  # can be True of False
@@ -116,7 +116,7 @@ def run(self, *, input_state, lead_time):
 
         lead_time = to_timedelta(lead_time)
 
-        # This may be used but Ouput objects to compute the step
+        # This may be used but Output objects to compute the step
         self.lead_time = lead_time
         self.time_step = self.checkpoint.timestep