diff --git a/src/calibre/customize/ui.py b/src/calibre/customize/ui.py
index 8397827fbb..14d22d5017 100644
--- a/src/calibre/customize/ui.py
+++ b/src/calibre/customize/ui.py
@@ -151,13 +151,13 @@ def reread_filetype_plugins():
 
 
 def _run_filetype_plugins(path_to_file, ft=None, occasion='preprocess'):
-    occasion = {'import':_on_import, 'preprocess':_on_preprocess,
+    occasion_plugins = {'import':_on_import, 'preprocess':_on_preprocess,
                 'postprocess':_on_postprocess}[occasion]
     customization = config['plugin_customization']
     if ft is None:
         ft = os.path.splitext(path_to_file)[-1].lower().replace('.', '')
     nfp = path_to_file
-    for plugin in occasion.get(ft, []):
+    for plugin in occasion_plugins.get(ft, []):
         if is_disabled(plugin):
             continue
         plugin.site_customization = customization.get(plugin.name, '')