diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index 450ea77669..5bec43ab28 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -1254,7 +1254,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         '''
         Set metadata for the book `id` from the `Metadata` object `mi`
         '''
-        if hasattr(mi, 'to_book_metadata'):
+        if callable(getattr(mi, 'to_book_metadata', None)):
             # Handle code passing in a OPF object instead of a Metadata object
             mi = mi.to_book_metadata()