diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 5449ef1474..e11c81d642 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -475,6 +475,10 @@ def main() -> None:
     with LoggingContext("main"):
         # check base requirements
         check_requirements()
+
+        # Set up VizTracer for debugging (if enabled)
+        setup_viztracer()
+
         hs = setup(sys.argv[1:])
 
         # redirect stdio to the logs, if configured.