diff --git a/src/main.py b/src/main.py
index 1d1fda9..1214fbe 100644
--- a/src/main.py
+++ b/src/main.py
@@ -73,7 +73,8 @@ def copy_excel_file(source_path, destination_path, passwords):
         source_sheet = source_wb[sheet_name]
         
         # Create new sheet in destination workbook
-        if source_sheet.sheet_type == 'chartsheet':
+        from openpyxl.chartsheet import Chartsheet
+        if isinstance(source_sheet, Chartsheet):
             # For chartsheets, we need to create a worksheet instead
             dest_sheet = dest_wb.create_sheet(title=sheet_name)