diff --git a/passerelle/contrib/toulouse_axel/models.py b/passerelle/contrib/toulouse_axel/models.py
index 2713bb8a..e71f9df2 100644
--- a/passerelle/contrib/toulouse_axel/models.py
+++ b/passerelle/contrib/toulouse_axel/models.py
@@ -747,7 +747,7 @@ class ToulouseAxel(BaseResource):
         example_pattern='{regie_id}/invoices',
         description=_("Get invoices to pay"),
         parameters={
-            'NameID': {'description': _('Publik ID')},
+            'NameID': {'description': _('Publik ID'), 'blank': False},
             'regie_id': {'description': _('Regie identifier'), 'example_value': '42-PERISCOL'},
         },
     )
diff --git a/tests/test_toulouse_axel.py b/tests/test_toulouse_axel.py
index b773f6e6..53ea46ea 100644
--- a/tests/test_toulouse_axel.py
+++ b/tests/test_toulouse_axel.py
@@ -2063,6 +2063,10 @@ def test_invoices_endpoint_axel_error(app, resource):
     assert resp.json['err_desc'] == "Axel error: FooBar"
     assert resp.json['err'] == 'error'
 
+    resp = app.get('/toulouse-axel/test/regie/MAREGIE/invoices?NameID=', status=400)
+    assert 'InvalidParameterValue' in resp.json['err_class']
+    assert resp.json['err'] == 1
+
 
 def test_invoices_endpoint_no_result(app, resource):
     resp = app.get('/toulouse-axel/test/regie/MAREGIE/invoices?NameID=yyy')