diff --git a/scrapy/utils/sitemap.py b/scrapy/utils/sitemap.py
index 1520a4ff0..03b7bf3b1 100644
--- a/scrapy/utils/sitemap.py
+++ b/scrapy/utils/sitemap.py
@@ -97,10 +97,11 @@ class Sitemap:
 
     @staticmethod
     def _get_tag_name(elem: lxml.etree._Element) -> str:
-        if TYPE_CHECKING:
-            assert isinstance(elem.tag, str)
-        _, _, localname = elem.tag.partition("}")
-        return localname or elem.tag
+        tag = elem.tag
+        if not isinstance(tag, str):
+            return ""
+        _, _, localname = tag.partition("}")
+        return localname or tag
 
 
 def sitemap_urls_from_robots(
diff --git a/tests/test_utils_sitemap.py b/tests/test_utils_sitemap.py
index 3599c4824..ac57e1739 100644
--- a/tests/test_utils_sitemap.py
+++ b/tests/test_utils_sitemap.py
@@ -311,3 +311,14 @@ def test_xml_entity_expansion():
     """
     )
     assert list(s) == [{"loc": "http://127.0.0.1:8000/"}]
+
+
+def test_sitemap_non_string_tag():
+    """With recover=True and resolve_entities=False, libxml2 >= 2.14.6 (used
+    by lxml >= 6.1.1) preserves undeclared entity reference nodes whose
+    .tag is a non-string ``Cython function`` object instead of a ``str``.
+    _get_tag_name must handle this gracefully instead of raising
+    AttributeError.
+    """
+    results = list(Sitemap(b"<url>&k;"))
+    assert results == []