diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index d2654577b9..5f66297322 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -706,6 +706,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         formats = row[fm['formats']]
         if not formats:
             formats = None
+        else:
+            formats = formats.split(',')
         mi.formats = formats
         tags = row[fm['tags']]
         if tags: