diff --git a/invenio_rdm_records/fixtures/vocabularies.py b/invenio_rdm_records/fixtures/vocabularies.py
index 6746aa844..cf7467baa 100644
--- a/invenio_rdm_records/fixtures/vocabularies.py
+++ b/invenio_rdm_records/fixtures/vocabularies.py
@@ -3,6 +3,7 @@
 # Copyright (C) 2021-2024 CERN.
 # Copyright (C) 2021-2022 Northwestern University.
 # Copyright (C) 2024 TU Wien.
+# Copyright (C) 2024 KTH Royal Institute of Technology.
 #
 # Invenio-RDM-Records is free software; you can redistribute it and/or modify
 # it under the terms of the MIT License; see LICENSE file for more details.
@@ -71,7 +72,7 @@ def map_row(self, header, row):
     def __iter__(self):
         """Iterate over records."""
         with open(self._data_file) as fp:
-            dialect = csv.Sniffer().sniff(fp.read(1024))
+            dialect = csv.Sniffer().sniff(fp.read(4096))
             fp.seek(0)
             reader = csv.reader(fp, dialect)
             header = next(reader)