Close issue #6210: Implement PEP 409

1 files changed, 4 insertions, 4 deletions

diff --git a/Lib/traceback.py b/Lib/traceback.py
index 8d4e96edcb..35858af1cc 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -120,14 +120,14 @@ def _iter_chain(exc, custom_tb=None, seen=None):
     seen.add(exc)
     its = []
     cause = exc.__cause__
-    if cause is not None and cause not in seen:
-        its.append(_iter_chain(cause, None, seen))
-        its.append([(_cause_message, None)])
-    else:
+    if cause is Ellipsis:
         context = exc.__context__
         if context is not None and context not in seen:
             its.append(_iter_chain(context, None, seen))
             its.append([(_context_message, None)])
+    elif cause is not None and cause not in seen:
+        its.append(_iter_chain(cause, False, seen))
+        its.append([(_cause_message, None)])
     its.append([(exc, custom_tb or exc.__traceback__)])
     # itertools.chain is in an extension module and may be unavailable
     for it in its: