diff --git a/TrainerClass.py b/TrainerClass.py
index 237ac41..e8d0389 100644
--- a/TrainerClass.py
+++ b/TrainerClass.py
@@ -372,7 +372,7 @@ class eNoseTrainer:
                                     "mse": mse,
                                     "mae": mae,
                                     "rmse": rmse,
-                                    "num_params": sum(t.count("\n") for t in optimized_model.get_booster().get_dump(dump_format="json"))
+                                    "num_params": None if model_params.get('multi_strategy') == 'multi_output_tree' else sum(t.count("\n") for t in optimized_model.get_booster().get_dump())
                                     }] )
                 self.ledger = pd.concat([self.ledger, newrow], ignore_index=True)
                 self.bar.update()
@@ -430,7 +430,7 @@ class eNoseTrainer:
                                     "mse": mse,
                                     "mae": mae,
                                     "rmse": rmse,
-                                    "num_params": sum(t.count("\n") for t in optimized_model.get_booster().get_dump(dump_format="json"))
+                                    "num_params": None if model_params.get('multi_strategy') == 'multi_output_tree' else sum(t.count("\n") for t in optimized_model.get_booster().get_dump())
 
                                     }] )
                 self.ledger = pd.concat([self.ledger, newrow], ignore_index=True)