diff --git a/odoo/addons/base/i18n/base.pot b/odoo/addons/base/i18n/base.pot
index 0418e6dd0df..837ad5bde12 100644
--- a/odoo/addons/base/i18n/base.pot
+++ b/odoo/addons/base/i18n/base.pot
@@ -18228,6 +18228,12 @@ msgstr ""
 msgid "Invalid 'group by' parameter"
 msgstr ""
 
+#. module: base
+#: code:addons/base/models/ir_default.py:0
+#, python-format
+msgid "Invalid JSON format in Default Value field."
+msgstr ""
+
 #. module: base
 #. odoo-python
 #: code:addons/base/models/ir_ui_view.py:0
diff --git a/odoo/addons/base/models/ir_default.py b/odoo/addons/base/models/ir_default.py
index 1026f846382..3c5e6fe36bd 100644
--- a/odoo/addons/base/models/ir_default.py
+++ b/odoo/addons/base/models/ir_default.py
@@ -22,6 +22,14 @@ class IrDefault(models.Model):
     condition = fields.Char('Condition', help="If set, applies the default upon condition.")
     json_value = fields.Char('Default Value (JSON format)', required=True)
 
+    @api.constrains('json_value')
+    def _check_json_format(self):
+        for record in self:
+            try:
+                json.loads(record.json_value)
+            except json.JSONDecodeError:
+                raise ValidationError(_('Invalid JSON format in Default Value field.'))
+
     @api.model_create_multi
     def create(self, vals_list):
         self.clear_caches()
diff --git a/odoo/addons/base/tests/test_ir_default.py b/odoo/addons/base/tests/test_ir_default.py
index 4981a03d9a9..1d05722db52 100644
--- a/odoo/addons/base/tests/test_ir_default.py
+++ b/odoo/addons/base/tests/test_ir_default.py
@@ -143,3 +143,13 @@ class TestIrDefault(TransactionCase):
             IrDefault.with_context(allowed_company_ids=company_b_a.ids)._get_model_defaults('res.partner')['ref'],
             'CBDefault',
         )
+
+    def test_json_format_invalid(self):
+        """ check the _check_json_format constraint """
+        IrDefault = self.env['ir.default']
+        field_id = self.env['ir.model.fields'].search([('model', '=', 'res.partner'), ('name', '=', 'ref')])
+        with self.assertRaises(ValidationError):
+            IrDefault.create({
+                'field_id': field_id.id,
+                'json_value': '{"name":"John", }',
+            })