diff --git a/tractor/_root.py b/tractor/_root.py
index d7b3359b..3d029808 100644
--- a/tractor/_root.py
+++ b/tractor/_root.py
@@ -456,6 +456,14 @@ async def open_root_actor(
         raddrs.extend(trans_bind_addrs)
         # TODO, remove once we have also removed all usage;
         # eventually all (root-)registry apis should expect > 1 addr.
+        root_mailbox = raddrs[0]
+        # if not isinstance(root_mailbox, tuple):
+        #     from .devx import mk_pdb
+        #     mk_pdb().set_trace()
+        #     raise TypeError(
+        #         f'Root mailbox addr must be a `tuple`?\n'
+        #         f'{root_mailbox!r}\n'
+        #     )
         _state._runtime_vars['_root_mailbox'] = raddrs[0]
 
         # Start up main task set via core actor-runtime nurseries.