diff --git a/mia_processes/bricks/preprocess/others/processing.py b/mia_processes/bricks/preprocess/others/processing.py
index e01d57c7a..e70305363 100644
--- a/mia_processes/bricks/preprocess/others/processing.py
+++ b/mia_processes/bricks/preprocess/others/processing.py
@@ -1681,7 +1681,11 @@ def __init__(self):
         self.add_trait(
             "labels",
             traits.List(
-                traits.Int(), output=False, optional=False, desc=labels_desc
+                traits.Int(),
+                output=False,
+                optional=True,
+                desc=labels_desc,
+                default=[1],
             ),
         )
         self.add_trait(
diff --git a/mia_processes/bricks/tools/tools.py b/mia_processes/bricks/tools/tools.py
index 3be46acd3..20c241d0c 100644
--- a/mia_processes/bricks/tools/tools.py
+++ b/mia_processes/bricks/tools/tools.py
@@ -1201,7 +1201,6 @@ def list_outputs(self, is_plugged=None):
                 filters = self.rois_list
 
             list_out = []
-            print("all_ref_files", all_ref_files)
             for ref_file in all_ref_files:
                 for _filter in filters:
                     if self.starts_with is True and ref_file.startswith(
@@ -1219,7 +1218,6 @@ def list_outputs(self, is_plugged=None):
                         list_out.append(
                             os.path.join(roi_raw_data_dir, ref_file)
                         )
-                        print("ref_file", ref_file)
                         self.dict4runtime[
                             os.path.join(self.lib_dir, ref_file)
                         ] = os.path.join(roi_raw_data_dir, ref_file)