diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index 38be2cd437f200..d1161c0b4a2b44 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -247,6 +247,13 @@ def check_element(element):
         self.assertRegex(repr(element), r"^<Element 't\xe4g' at 0x.*>$")
         element = ET.Element("tag", key="value")
 
+        # Verify type checking for ElementTree constructor
+
+        with self.assertRaises(TypeError):
+            tree = ET.ElementTree("")
+        with self.assertRaises(TypeError):
+            tree = ET.ElementTree(ET.ElementTree())
+
         # Make sure all standard element methods exist.
 
         def check_method(method):
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 44ab5d18624e73..4dabb211d0b863 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -527,7 +527,9 @@ class ElementTree:
 
     """
     def __init__(self, element=None, file=None):
-        # assert element is None or iselement(element)
+        if element is not None and not iselement(element):
+            raise TypeError(f"element must be etree.Element, "
+                            f"not {type(element).__name__}")
         self._root = element # first node
         if file:
             self.parse(file)
@@ -543,7 +545,9 @@ def _setroot(self, element):
         with the given element.  Use with care!
 
         """
-        # assert iselement(element)
+        if not iselement(element):
+            raise TypeError(f"element must be etree.Element, "
+                            f"not {type(element).__name__}")
         self._root = element
 
     def parse(self, source, parser=None):