diff --git a/src/calibre/ebooks/metadata/book/json_codec.py b/src/calibre/ebooks/metadata/book/json_codec.py
index 4b292925f3..c01a36d5ac 100644
--- a/src/calibre/ebooks/metadata/book/json_codec.py
+++ b/src/calibre/ebooks/metadata/book/json_codec.py
@@ -69,7 +69,7 @@ def object_to_unicode(obj, enc=preferred_encoding):
     if isbytestring(obj):
         return dec(obj)
     if isinstance(obj, (list, tuple)):
-        return [dec(x) if isbytestring(x) else x for x in obj]
+        return [dec(x) if isbytestring(x) else object_to_unicode(x) for x in obj]
     if isinstance(obj, dict):
         ans = {}
         for k, v in obj.items():