diff --git a/isbnfromiabot/isbn_ia_to_13.py b/isbnfromiabot/isbn_ia_to_13.py
index b25d3a82..42ef789b 100644
--- a/isbnfromiabot/isbn_ia_to_13.py
+++ b/isbnfromiabot/isbn_ia_to_13.py
@@ -31,7 +31,7 @@ def run(self) -> None:
                     source_records = _json.get("source_records", None)
                 else:
                     continue
-                regex = "ia:isbn_\d{13}"
+                regex = "ia:isbn_[0-9]{13}"
                 isbn_13 = False
                 for source_record in source_records:
                     if re.fullmatch(regex, source_record):