diff --git a/aiogram/utils/callback_data.py b/aiogram/utils/callback_data.py
index 23ff3dd0..bb7d6862 100644
--- a/aiogram/utils/callback_data.py
+++ b/aiogram/utils/callback_data.py
@@ -34,7 +34,7 @@ class CallbackData:
         elif len(sep) != 1:
             raise ValueError(f"Length of sep should be equals to 1")
         elif sep in prefix:
-            raise ValueError(f"Symbol '{self.sep}' can't be used in prefix")
+            raise ValueError(f"Symbol '{sep}' can't be used in prefix")
         elif not parts:
             raise TypeError('Parts is not passed!')