diff --git a/dbus_next/aio/message_bus.py b/dbus_next/aio/message_bus.py
index 3ffa4e9..83982d9 100644
--- a/dbus_next/aio/message_bus.py
+++ b/dbus_next/aio/message_bus.py
@@ -59,7 +59,7 @@ def write_callback(self):
                     # wait for writable
                     return
         except Exception as e:
-            if self.fut is not None:
+            if self.fut is not None and not self.fut.done():
                 self.fut.set_exception(e)
             self.bus._finalize(e)