diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index c606db1b85..59e5c34cdd 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -1634,7 +1634,7 @@ class Cache(object):
 
     @write_api
     def create_custom_column(self, label, name, datatype, is_multiple, editable=True, display={}):
-        self.backend.create_custom_column(label, name, datatype, is_multiple, editable=editable, display=display)
+        return self.backend.create_custom_column(label, name, datatype, is_multiple, editable=editable, display=display)
 
     @write_api
     def set_custom_column_metadata(self, num, name=None, label=None, is_editable=None,
diff --git a/src/calibre/library/cli.py b/src/calibre/library/cli.py
index 08775a9138..69e4bc811f 100644
--- a/src/calibre/library/cli.py
+++ b/src/calibre/library/cli.py
@@ -719,7 +719,7 @@ def command_export(args, dbpath):
 
 def do_add_custom_column(db, label, name, datatype, is_multiple, display):
     num = db.create_custom_column(label, name, datatype, is_multiple, display=display)
-    prints('Custom column created with id: %d'%num)
+    prints('Custom column created with id: %s'%num)
 
 def add_custom_column_option_parser():
     from calibre.library.custom_columns import CustomColumns