diff --git a/photo_mask/photo_mask.py b/photo_mask/photo_mask.py
index be062d5..9c82182 100644
--- a/photo_mask/photo_mask.py
+++ b/photo_mask/photo_mask.py
@@ -68,11 +68,11 @@ def find_boxes(content, layout, offset=0, length=None, improve=False, image_path
             # 如果出现其他错误，抛出
             raise e
         if extra_content:
-            contents = extra_content.append(content)
+            extra_content.append(content)
         else:
-            contents = [content]
+            extra_content = [content]
         for layout in layouts:
-            for c in contents:
+            for c in extra_content:
                 if c in layout[1]:
                     temp_box = find_boxes(content, layout)[0]
                     if temp_box: