From aa5e3f6884a91b0fd67fae0f861a51d6a534e3bd Mon Sep 17 00:00:00 2001
From: Afonso Coutinho <afonso@omelhorsite.pt>
Date: Wed, 3 Jun 2026 01:00:10 +0100
Subject: [PATCH] fix: is_markitdown_format crashes on a non-string path
 (#1618)

---
 src/markitdown_runtime.py                 |  2 ++
 tests/test_markitdown_format_nonstring.py | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 tests/test_markitdown_format_nonstring.py

diff --git a/src/markitdown_runtime.py b/src/markitdown_runtime.py
index f8338d3..ff30b01 100644
--- a/src/markitdown_runtime.py
+++ b/src/markitdown_runtime.py
@@ -26,6 +26,8 @@ MARKITDOWN_EXTS = frozenset({".docx", ".pptx", ".xlsx", ".xls", ".epub"})
 
 def is_markitdown_format(path: str) -> bool:
     """True if the file extension is one we route through markitdown."""
+    if not isinstance(path, str):
+        return False
     return os.path.splitext(path)[1].lower() in MARKITDOWN_EXTS
 
 
diff --git a/tests/test_markitdown_format_nonstring.py b/tests/test_markitdown_format_nonstring.py
new file mode 100644
index 0000000..2641948
--- /dev/null
+++ b/tests/test_markitdown_format_nonstring.py
@@ -0,0 +1,16 @@
+"""Regression: is_markitdown_format must tolerate a non-string path.
+
+It did `os.path.splitext(path)`, which raises TypeError on None / non-string.
+"""
+from src.markitdown_runtime import is_markitdown_format
+
+
+def test_non_string_returns_false():
+    assert is_markitdown_format(None) is False
+    assert is_markitdown_format(123) is False
+    assert is_markitdown_format(["a.docx"]) is False
+
+
+def test_valid_extension_detected():
+    assert is_markitdown_format("report.docx") is True
+    assert is_markitdown_format("notes.txt") is False