diff --git a/pymisp/api.py b/pymisp/api.py
index c831856..81815ac 100644
--- a/pymisp/api.py
+++ b/pymisp/api.py
@@ -588,7 +588,7 @@ class PyMISP:
         :param break_on_duplicate: if True, check and reject if this object's attributes match an existing object's attributes; may require much time
         """
         event_id = get_uuid_or_id_from_abstract_misp(event)
-        params = {'breakOnDuplicate': True} if break_on_duplicate else {}
+        params = {'breakOnDuplicate': 1} if break_on_duplicate else {}
         r = self._prepare_request('POST', f'objects/add/{event_id}', data=misp_object, kw_params=params)
         new_object = self._check_json_response(r)
         if not (self.global_pythonify or pythonify) or 'errors' in new_object:
@@ -741,7 +741,7 @@ class PyMISP:
         r = self._prepare_request('HEAD', f'attributes/view/{attribute_id}')
         return self._check_head_response(r)
 
-    def add_attribute(self, event: Union[MISPEvent, int, str, UUID], attribute: Union[MISPAttribute, Iterable], pythonify: bool = False) -> Union[Dict, MISPAttribute, MISPShadowAttribute]:
+    def add_attribute(self, event: Union[MISPEvent, int, str, UUID], attribute: Union[MISPAttribute, Iterable], pythonify: bool = False, break_on_duplicate: bool = True) -> Union[Dict, MISPAttribute, MISPShadowAttribute]:
         """Add an attribute to an existing MISP event: https://www.misp-project.org/openapi/#tag/Attributes/operation/addAttribute
 
         :param event: event to extend
@@ -749,9 +749,11 @@ class PyMISP:
             If a list is passed, the pythonified response is a dict with the following structure:
             {'attributes': [MISPAttribute], 'errors': {errors by attributes}}
         :param pythonify: Returns a PyMISP Object instead of the plain json output
+        :param break_on_duplicate: if False, do not fail if the attribute already exists, updates existing attribute instead (timestamp will be always updated)
         """
+        params = {'breakOnDuplicate': 0} if break_on_duplicate is not True else {}
         event_id = get_uuid_or_id_from_abstract_misp(event)
-        r = self._prepare_request('POST', f'attributes/add/{event_id}', data=attribute)
+        r = self._prepare_request('POST', f'attributes/add/{event_id}', data=attribute, kw_params=params)
         new_attribute = self._check_json_response(r)
         if isinstance(attribute, list):
             # Multiple attributes were passed at once, the handling is totally different
diff --git a/tests/testlive_comprehensive.py b/tests/testlive_comprehensive.py
index b12d216..bf511fe 100644
--- a/tests/testlive_comprehensive.py
+++ b/tests/testlive_comprehensive.py
@@ -1901,6 +1901,15 @@ class TestComprehensive(unittest.TestCase):
             similar_error = self.user_misp_connector.add_attribute(first, new_similar)
             self.assertEqual(similar_error['errors'][1]['errors']['value'][0], 'A similar attribute already exists for this event.')
 
+            # Test add attribute break_on_duplicate=False
+            time.sleep(5)
+            new_similar = MISPAttribute()
+            new_similar.value = '1.2.3.4'
+            new_similar.type = 'ip-dst'
+            new_similar = self.user_misp_connector.add_attribute(first, new_similar, break_on_duplicate=False)
+            self.assertTrue(isinstance(new_similar, MISPAttribute), new_similar)
+            self.assertGreater(new_similar.timestamp, new_attribute.timestamp)
+
             # Test add multiple attributes at once
             attr0 = MISPAttribute()
             attr0.value = '0.0.0.0'