diff --git a/src/viralhostrange/viralhostrangedb/business_process.py b/src/viralhostrange/viralhostrangedb/business_process.py
index c32a415f0bcb966777e5f036e005baeb8136168a..bbc93df2e98c10d9ce65d619b2ed1dad0fae1253 100755
--- a/src/viralhostrange/viralhostrangedb/business_process.py
+++ b/src/viralhostrange/viralhostrangedb/business_process.py
@@ -360,7 +360,7 @@ def __parse_file(file, importation_observer: ImportationObserver = None, sheet_n
                     start_at = id_col - 1 + start_at
                     header_set = set(header[1:])
                     if importation_observer:
-                        for header_col, h in reversed(list(enumerate(header[1:]))):
+                        for header_col, h in enumerate(header[1:]):
                             try:
                                 header_set.remove(h)
                             except KeyError: