diff --git a/src/calibre/gui2/library/models.py b/src/calibre/gui2/library/models.py
index 5490e96169..48ce5bbc45 100644
--- a/src/calibre/gui2/library/models.py
+++ b/src/calibre/gui2/library/models.py
@@ -966,6 +966,7 @@ class DeviceBooksModel(BooksModel): # {{{
         return len(self.map)
 
     def set_database(self, db):
+        self.custom_columns = {}
         self.db = db
         self.map = list(range(0, len(db)))