diff --git a/frappe/model/naming.py b/frappe/model/naming.py
index 359b8e2367..b8d6a6f8d7 100644
--- a/frappe/model/naming.py
+++ b/frappe/model/naming.py
@@ -283,7 +283,7 @@ def append_number_if_name_exists(doctype, value, fieldname="name", separator="-"
 	filters.update({fieldname: value})
 	exists = frappe.db.exists(doctype, filters)
 
-	regex = "^{value}{separator}\d+$".format(value=re.escape(value), separator=separator)
+	regex = "^{value}{separator}\\d+$".format(value=re.escape(value), separator=separator)
 
 	if exists:
 		last = frappe.db.sql("""SELECT `{fieldname}` FROM `tab{doctype}`