diff --git a/antarest/study/business/binding_constraint_management.py b/antarest/study/business/binding_constraint_management.py
index a382277bd5..ac012ed0e0 100644
--- a/antarest/study/business/binding_constraint_management.py
+++ b/antarest/study/business/binding_constraint_management.py
@@ -423,6 +423,7 @@ def constraint_model_adapter(constraint: Mapping[str, Any], version: int) -> Con
             "terms": constraint.get("terms", []),
         }
 
+        # TODO: Implement a model for version-specific fields. Output filters are sent regardless of the version.
         if version >= 840:
             constraint_output["filter_year_by_year"] = constraint.get("filter_year_by_year") or constraint.get(
                 "filter-year-by-year", ""
diff --git a/antarest/study/storage/variantstudy/model/command/create_binding_constraint.py b/antarest/study/storage/variantstudy/model/command/create_binding_constraint.py
index 5a832b7d29..8d666db596 100644
--- a/antarest/study/storage/variantstudy/model/command/create_binding_constraint.py
+++ b/antarest/study/storage/variantstudy/model/command/create_binding_constraint.py
@@ -75,13 +75,13 @@ class BindingConstraintProperties(BaseModel, extra=Extra.forbid, allow_populatio
     enabled: bool = True
     time_step: BindingConstraintFrequency = BindingConstraintFrequency.HOURLY
     operator: BindingConstraintOperator = BindingConstraintOperator.EQUAL
-    comments: t.Optional[str] = None
-    filter_year_by_year: t.Optional[str] = None
-    filter_synthesis: t.Optional[str] = None
+    comments: t.Optional[str] = ""
+    filter_year_by_year: t.Optional[str] = ""
+    filter_synthesis: t.Optional[str] = ""
 
 
 class BindingConstraintProperties870(BindingConstraintProperties):
-    group: t.Optional[str] = None
+    group: t.Optional[str] = "default"
 
 
 class BindingConstraintMatrices(BaseModel, extra=Extra.forbid, allow_population_by_field_name=True):
diff --git a/tests/variantstudy/model/command/test_manage_binding_constraints.py b/tests/variantstudy/model/command/test_manage_binding_constraints.py
index aab13307b1..fc124bdb40 100644
--- a/tests/variantstudy/model/command/test_manage_binding_constraints.py
+++ b/tests/variantstudy/model/command/test_manage_binding_constraints.py
@@ -92,6 +92,7 @@ def test_manage_binding_constraint(empty_study: FileStudy, command_context: Comm
         "name": "BD 2",
         "id": "bd 2",
         "enabled": False,
+        "comments": "",
         "area1.cluster": 50.0,
         "operator": "both",
         "type": "daily",
@@ -127,6 +128,7 @@ def test_manage_binding_constraint(empty_study: FileStudy, command_context: Comm
         "id": "bd 1",
         "enabled": False,
         "area1%area2": "800.0%30",
+        "comments": "",
         "operator": "both",
         "type": "weekly",
     }
@@ -151,6 +153,7 @@ def test_manage_binding_constraint(empty_study: FileStudy, command_context: Comm
         "id": "bd 2",
         "enabled": False,
         "area1.cluster": 50.0,
+        "comments": "",
         "operator": "both",
         "type": "daily",
     }
@@ -338,7 +341,7 @@ def test_revert(command_context: CommandContext):
             operator=BindingConstraintOperator.EQUAL,
             coeffs={"a": [0.3]},
             values=hourly_matrix_id,
-            comments=None,
+            comments="",
             command_context=command_context,
         )
     ]