1 files changed, 2 insertions, 1 deletions
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index b8081f197e..bfe9136fd8 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -486,7 +486,7 @@ def start_active_span_from_request(
 def start_active_span_from_edu(
     edu_content,
     operation_name,
-    references=[],
+    references: Optional[list] = None,
     tags=None,
     start_time=None,
     ignore_active_span=False,
@@ -501,6 +501,7 @@ def start_active_span_from_edu(
 
         For the other args see opentracing.tracer
     """
+    references = references or []
 
     if opentracing is None:
         return noop_context_manager()