diff --git a/sentry_sdk/client.py b/sentry_sdk/client.py
index ffd899b545..a8b3240171 100644
--- a/sentry_sdk/client.py
+++ b/sentry_sdk/client.py
@@ -622,7 +622,8 @@ def _prepare_event(
             )
         if previous_total_breadcrumbs is not None:
             event["breadcrumbs"] = AnnotatedValue(
-                event.get("breadcrumbs", []), {"len": previous_total_breadcrumbs}
+                event.get("breadcrumbs", {"values": []}),
+                {"len": previous_total_breadcrumbs},
             )
 
         # Postprocess the event here so that annotated types do