diff --git a/src/logic/dataclass.py b/src/logic/dataclass.py
index 0bd5151..f32f37b 100644
--- a/src/logic/dataclass.py
+++ b/src/logic/dataclass.py
@@ -75,6 +75,7 @@ class BookData:
     year: str | None = None
     pages: str | None = None
     library_location: int | None = None
+    in_apparat: bool | None = False
 
     def from_dict(self, data: dict):
         for key, value in data.items():