diff --git a/lib/galaxy/datatypes/sniff.py b/lib/galaxy/datatypes/sniff.py
index bac624937e96..392745b1c456 100644
--- a/lib/galaxy/datatypes/sniff.py
+++ b/lib/galaxy/datatypes/sniff.py
@@ -399,6 +399,9 @@ def guess_ext(fname_or_file_prefix: Union[str, "FilePrefix"], sniff_order, is_bi
     >>> fname = get_test_fname('Si.cif')
     >>> guess_ext(fname, sniff_order)
     'cif'
+    >>> fname = get_test_fname('LaMnO3.cif')
+    >>> guess_ext(fname, sniff_order)
+    'cif'
     >>> fname = get_test_fname('Si.xyz')
     >>> guess_ext(fname, sniff_order)
     'xyz'