diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index 5632b8b503c..bfc0d054ba8 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -312,6 +312,9 @@ def test_simpleops(self):
elem.extend([e])
self.serialize_check(elem, '')
elem.remove(e)
+ elem.extend(iter([e]))
+ self.serialize_check(elem, '')
+ elem.remove(e)
element = ET.Element("tag", key="value")
self.serialize_check(element, '') # 1
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 7a269001d6e..ac82ed80419 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -252,7 +252,7 @@ def extend(self, elements):
"""
for element in elements:
self._assert_is_element(element)
- self._children.extend(elements)
+ self._children.append(element)
def insert(self, index, subelement):
"""Insert *subelement* at position *index*."""
diff --git a/Misc/ACKS b/Misc/ACKS
index 73d35c2d86b..4f7c92c9dc0 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1363,6 +1363,7 @@ Matheus Vieira Portela
Davin Potts
Guillaume Pratte
Florian Preinstorfer
+Alex Prengère
Amrit Prem
Paul Prescod
Donovan Preston
diff --git a/Misc/NEWS.d/next/Library/2021-03-04-17-53-46.bpo-43399.Wn95u-.rst b/Misc/NEWS.d/next/Library/2021-03-04-17-53-46.bpo-43399.Wn95u-.rst
new file mode 100644
index 00000000000..0b8dffb2312
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-03-04-17-53-46.bpo-43399.Wn95u-.rst
@@ -0,0 +1,2 @@
+Fix ``ElementTree.extend`` not working on iterators when using the
+Python implementation