diff --git a/puremagic/main.py b/puremagic/main.py
index e2f6419..57f4816 100644
--- a/puremagic/main.py
+++ b/puremagic/main.py
@@ -270,7 +270,7 @@ def ext_from_filename(filename: os.PathLike | str) -> str:
     :return: the extension off the end (empty string if it can't find one)
     """
     try:
-        base, ext = str(filename).lower().rsplit(".", 1)
+        base, ext = os.path.basename(filename).lower().rsplit(".", 1)
     except ValueError:
         return ""
     ext = f".{ext}"
diff --git a/test/test_common_extensions.py b/test/test_common_extensions.py
index 0294b2b..f0d2154 100644
--- a/test/test_common_extensions.py
+++ b/test/test_common_extensions.py
@@ -202,6 +202,16 @@ def test_ext():
     assert ext == ".tar.bz2", ext
 
 
+@pytest.mark.parametrize("path_type", [str, Path])
+@pytest.mark.parametrize(
+    "filename, expected",
+    [("README", ""), ("report.PDF", ".pdf"), ("archive.tar.bz2", ".tar.bz2"), (".profile", ".profile")],
+)
+def test_ext_ignores_parent_directory_dots(path_type, filename, expected):
+    filename = path_type(os.path.join("directory.with.dots", filename))
+    assert puremagic.ext_from_filename(filename) == expected
+
+
 def test_cmd_options():
     """Test CLI options"""
     try: