diff --git a/packages/markitdown/src/markitdown/converters/_xlsx_converter.py b/packages/markitdown/src/markitdown/converters/_xlsx_converter.py
index 9f794a3b7..80b143cd3 100644
--- a/packages/markitdown/src/markitdown/converters/_xlsx_converter.py
+++ b/packages/markitdown/src/markitdown/converters/_xlsx_converter.py
@@ -208,8 +208,12 @@ def accepts(
         mimetype = (stream_info.mimetype or "").lower()
         extension = (stream_info.extension or "").lower()
 
-        if extension in ACCEPTED_XLS_FILE_EXTENSIONS:
-            return True
+        # Some upstream systems label every legacy Office Compound File as
+        # application/vnd.ms-excel, including Word .doc files. When the
+        # extension is known, use it as the discriminator so a .doc is not
+        # handed to xlrd. MIME type remains a fallback for extensionless input.
+        if extension:
+            return extension in ACCEPTED_XLS_FILE_EXTENSIONS
 
         for prefix in ACCEPTED_XLS_MIME_TYPE_PREFIXES:
             if mimetype.startswith(prefix):
diff --git a/packages/markitdown/tests/test_module_misc.py b/packages/markitdown/tests/test_module_misc.py
index 23d6f49aa..d482e5b39 100644
--- a/packages/markitdown/tests/test_module_misc.py
+++ b/packages/markitdown/tests/test_module_misc.py
@@ -363,6 +363,27 @@ def test_exceptions() -> None:
     assert type(exc_info.value.attempts[0].converter).__name__ == "PptxConverter"
 
 
+def test_legacy_doc_with_excel_mimetype_is_not_sent_to_xls_converter(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    markitdown = MarkItDown()
+    monkeypatch.setattr(
+        markitdown._magika,
+        "identify_stream",
+        MagicMock(return_value=SimpleNamespace(status="unknown")),
+    )
+
+    with pytest.raises(UnsupportedFormatException):
+        markitdown.convert_stream(
+            io.BytesIO(b"\x00\x01\x02\x03" * 64),
+            stream_info=StreamInfo(
+                filename="legacy.doc",
+                extension=".doc",
+                mimetype="application/vnd.ms-excel",
+            ),
+        )
+
+
 def test_markitdown_llm_parameters() -> None:
     """Test that LLM parameters are correctly passed to the client."""
     mock_client = MagicMock()
diff --git a/packages/markitdown/tests/test_xlsx.py b/packages/markitdown/tests/test_xlsx.py
index 928262295..4bff32801 100644
--- a/packages/markitdown/tests/test_xlsx.py
+++ b/packages/markitdown/tests/test_xlsx.py
@@ -446,6 +446,19 @@ def entity(name: str, content: bytes) -> bytes:
     render.assert_not_called()
 
 
+def test_xls_acceptance_prefers_known_extension_over_mimetype() -> None:
+    converter = XlsConverter()
+    excel_mimetype = "application/vnd.ms-excel"
+
+    assert converter.accepts(
+        io.BytesIO(), StreamInfo(extension=".xls", mimetype=excel_mimetype)
+    )
+    assert converter.accepts(io.BytesIO(), StreamInfo(mimetype=excel_mimetype))
+    assert not converter.accepts(
+        io.BytesIO(), StreamInfo(extension=".doc", mimetype=excel_mimetype)
+    )
+
+
 def test_missing_dependencies_and_legacy_xls_stay_separate(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None: