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..2ff916b42 100644
--- a/tests/test_utils_sitemap.py
+++ b/tests/test_utils_sitemap.py
@@ -311,3 +311,21 @@ def test_xml_entity_expansion():
     """
     )
     assert list(s) == [{"loc": "http://127.0.0.1:8000/"}]
+
+
+def test_sitemap_non_string_tag():
+    """Regression test for non-string elem.tag crashing _get_tag_name.
+
+    When parsing malformed XML with recover=True and resolve_entities=False,
+    libxml2 can produce nodes whose .tag is not a string (e.g. a Cython
+    function). _get_tag_name must handle this gracefully instead of raising
+    AttributeError.
+    """
+    from base64 import b64decode
+
+    data = b64decode(
+        "PHVybGluaz48dXI8dXJsPgAAAAAAAAAEaW5rIHhtbG5zOnhodG1sPSJoZGwiIGhyZWY9ImhsPjxsaW4mazsiaGxybGtuazx4aHRtbDpsaW5rIHhtbG5zOnhodG1sPSJoZGwiIGhyZWY9ImhsaW5rbCIgaHJlZj0iaGw+PHhodG1sZGxzZXQ+"
+    )
+    # Must not raise AttributeError
+    results = list(Sitemap(data))
+    assert isinstance(results, list)