diff --git a/passerelle/contrib/greco/formdata.py b/passerelle/contrib/greco/formdata.py
index ad18f0a8..e66e3fdf 100644
--- a/passerelle/contrib/greco/formdata.py
+++ b/passerelle/contrib/greco/formdata.py
@@ -117,13 +117,15 @@ class FormData:
                 self.fields[fieldname] = value
                 if isinstance(value, datetime):
                     value = value.strftime('%Y-%m-%dT%H:%M:%S')
-                if '_' not in fieldname:
-                    self.json[fieldname] = value
-                    continue
-                key, subkey = fieldname.split('_')
-                if key not in self.json:
-                    self.json[key] = {}
-                self.json[key][subkey] = value
+            else:
+                value = ''
+            if '_' not in fieldname:
+                self.json[fieldname] = value
+                continue
+            key, subkey = fieldname.split('_')
+            if key not in self.json:
+                self.json[key] = {}
+            self.json[key][subkey] = value
 
         # https://dev.entrouvert.org/issues/75259
         danger = self.json.get('danger', '')
diff --git a/tests/test_greco.py b/tests/test_greco.py
index 3da5c787..6f5c0f0e 100644
--- a/tests/test_greco.py
+++ b/tests/test_greco.py
@@ -246,6 +246,8 @@ def test_greco_rest_create_ok(app, rest_conn):
     assert json_part.headers[b'Content-Type'] == b'application/json'
     demande_creation = json.loads(json_part.content)
     assert demande_creation['application'] == '69999'
+    assert demande_creation['beneficiaire']['fax'] == ''
+    assert demande_creation['beneficiaire']['numerovoie'] == ''
     assert demande_creation['localisation']['xgeoloc'] == '50.89491'
     assert demande_creation['localisation']['ygeoloc'] == '4.34151'
     assert demande_creation['transmetteur']['nom'] == 'Vertommen'