diff --git a/ipykernel/iostream.py b/ipykernel/iostream.py
index 50f86d243..a1a54a84e 100644
--- a/ipykernel/iostream.py
+++ b/ipykernel/iostream.py
@@ -455,7 +455,12 @@ def flush(self):
 
         send will happen in the background thread
         """
-        if self.pub_thread and self.pub_thread.thread is not None and self.pub_thread.thread.is_alive():
+        if (
+                self.pub_thread
+                and self.pub_thread.thread is not None
+                and self.pub_thread.thread.is_alive()
+                and self.pub_thread.thread.ident != threading.current_thread().ident
+        ):
             # request flush on the background thread
             self.pub_thread.schedule(self._flush)
             # wait for flush to actually get through, if we can.