diff --git a/python/monarch/_src/actor/actor_mesh.py b/python/monarch/_src/actor/actor_mesh.py
index c0503a9e4..16164968c 100644
--- a/python/monarch/_src/actor/actor_mesh.py
+++ b/python/monarch/_src/actor/actor_mesh.py
@@ -274,7 +274,7 @@ def filter(self, record: Any) -> bool:
         fn = _monarch_actor().per_actor_logging_prefix
         ctx = _context.get(None)
         if ctx is not None and fn is not None:
-            record.msg = fn(ctx.actor_instance) + record.msg
+            record.msg = f"{fn(ctx.actor_instance)}{record.msg}"
         return True