diff --git a/src/calibre/customize/ui.py b/src/calibre/customize/ui.py
index 967c5ab47a..156eb046a4 100644
--- a/src/calibre/customize/ui.py
+++ b/src/calibre/customize/ui.py
@@ -253,7 +253,8 @@ def _run_filetype_plugins(path_to_file, ft=None, occasion='preprocess'):
 
 def initialize_plugin(plugin, path_to_zip_file):
     try:
-        return plugin(path_to_zip_file)
+        p = plugin(path_to_zip_file)
+        p.initialize()
     except Exception:
         print 'Failed to initialize plugin:', plugin.name, plugin.version
         tb = traceback.format_exc()