diff --git a/tractor/_root.py b/tractor/_root.py
index 6ad84f1..c5b8f17 100644
--- a/tractor/_root.py
+++ b/tractor/_root.py
@@ -127,8 +127,7 @@ async def open_root_actor(
             "Debug mode is only supported for the `trio` backend!"
         )
 
-    loglevel = log._default_loglevel = loglevel.upper()
-    assert loglevel
+    loglevel = (loglevel or log._default_loglevel).upper()
     log.get_console_log(loglevel)
 
     # make a temporary connection to see if an arbiter exists