diff --git a/invenio_stats/aggregations.py b/invenio_stats/aggregations.py
index 737cea2..21a1b17 100644
--- a/invenio_stats/aggregations.py
+++ b/invenio_stats/aggregations.py
@@ -341,7 +341,8 @@ def agg_iter(self, dt):
                 ignore_cache=True,
             )
             for aggregation in results.aggregations["terms"].buckets:
-                doc = aggregation.top_hit.hits.hits[0]["_source"]
+                doc = aggregation.top_hit.hits.hits[0]["_source"].to_dict()
+                aggregation = aggregation.to_dict()
                 interval_date = datetime.strptime(
                     doc["timestamp"], "%Y-%m-%dT%H:%M:%S"
                 ).replace(**dict.fromkeys(INTERVAL_ROUNDING[self.interval], 0))