diff --git a/src/fideslang/models.py b/src/fideslang/models.py
index b5c177a..599b8fd 100644
--- a/src/fideslang/models.py
+++ b/src/fideslang/models.py
@@ -991,8 +991,9 @@ class PrivacyDeclaration(BaseModel):
     features: List[str] = Field(
         default_factory=list, description="The features of processing personal data."
     )
-    flexible_legal_basis_for_processing: Optional[bool] = Field(
+    flexible_legal_basis_for_processing: bool = Field(
         description="Whether the legal basis for processing is 'flexible' (i.e. can be overridden in a privacy notice) for this declaration.",
+        default=True,
     )
     legal_basis_for_processing: Optional[LegalBasisForProcessingEnum] = Field(
         description="The legal basis under which personal data is processed for this purpose."
diff --git a/tests/fideslang/test_models.py b/tests/fideslang/test_models.py
index 98bfb29..a922128 100644
--- a/tests/fideslang/test_models.py
+++ b/tests/fideslang/test_models.py
@@ -434,6 +434,17 @@ def test_expanded_system(self):
             ],
         )
 
+    def test_flexible_legal_basis_default(self):
+        pd = PrivacyDeclaration(
+            data_categories=[],
+            data_qualifier="aggregated_data",
+            data_subjects=[],
+            data_use="provide",
+            ingress=["user"],
+            name="declaration-name",
+        )
+        assert pd.flexible_legal_basis_for_processing
+
     @mark.parametrize(
         "deprecated_field,value",
         [