diff --git a/src/calibre/db/lazy.py b/src/calibre/db/lazy.py
index 5e8c4d4d8a..059ee18762 100644
--- a/src/calibre/db/lazy.py
+++ b/src/calibre/db/lazy.py
@@ -236,7 +236,7 @@ def composite_getter(mi, field, dbref, book_id, cache, formatter, template_cache
         except Exception:
             import traceback
             traceback.print_exc()
-            return 'ERROR WHILE EVALUATING ' + field
+            return 'ERROR WHILE EVALUATING: %s' % field
         return ret
 
 def virtual_libraries_getter(dbref, book_id, cache):