diff --git a/citadel/indico_citadel/util.py b/citadel/indico_citadel/util.py
index 42460a5..92380b0 100644
--- a/citadel/indico_citadel/util.py
+++ b/citadel/indico_citadel/util.py
@@ -155,7 +155,6 @@ def format_aggregations(aggregations, filters):
         key: {
             'label': str(filters[key]),
             'buckets': [{
-                **bucket,
                 'key': bucket['most_common']['buckets'][0]['key'] if 'most_common' in bucket else bucket['key'],
                 'count': bucket['doc_count']
             } for bucket in value['buckets']]
diff --git a/citadel/indico_citadel/util_test.py b/citadel/indico_citadel/util_test.py
index 431123a..7cb3e9c 100644
--- a/citadel/indico_citadel/util_test.py
+++ b/citadel/indico_citadel/util_test.py
@@ -7,7 +7,7 @@
 
 import pytest
 
-from indico_citadel.util import format_query, remove_none_entries
+from indico_citadel.util import _flatten, format_query, remove_none_entries
 
 
 @pytest.mark.parametrize(('query', 'expected'), [
@@ -39,3 +39,13 @@ def test_query_placeholders(query, expected):
 ])
 def test_remove_none_entries(val, expected):
     assert remove_none_entries(val) == expected
+
+
+@pytest.mark.parametrize(('val', 'expected'), [
+    ({'person': {'name': {'buckets': []}, 'affiliation': {'buckets': []}}, 'other': {'other': {'buckets': []}}},
+     {'person_name', 'person_affiliation', 'other_other'}),
+    ({'other': {'other': {'other': {'other': {'buckets': []}}}}},
+     {'other_other_other_other'})
+])
+def test_flatten(val, expected):
+    assert {key for key, _ in _flatten(val)} == expected