diff --git a/src/dandi_s3_log_parser/_log_utils.py b/src/dandi_s3_log_parser/_log_utils.py
index 27328ce..8323a84 100644
--- a/src/dandi_s3_log_parser/_log_utils.py
+++ b/src/dandi_s3_log_parser/_log_utils.py
@@ -28,9 +28,10 @@ def find_all_known_operation_types(
         leave=True,
     ):
         operation_types_per_file = {
-            raw_log_line[:500].split(" ")[7]
+            field[7]
             for buffered_text_reader in BufferedTextReader(file_path=raw_s3_log_file_path)
             for raw_log_line in buffered_text_reader
+            if len((field := raw_log_line[:500].split(" "))) > 7
         }
 
         unique_operation_types.update(operation_types_per_file)