diff --git a/src/calibre/ebooks/metadata/meta.py b/src/calibre/ebooks/metadata/meta.py
index c6d3cf479a..f2c31a538d 100644
--- a/src/calibre/ebooks/metadata/meta.py
+++ b/src/calibre/ebooks/metadata/meta.py
@@ -83,7 +83,7 @@ def get_metadata(stream, stream_type='lrf', use_libprs_metadata=False):
     return base
 
 def set_metadata(stream, mi, stream_type='lrf'):
-    if stream_type: 
+    if stream_type:
         stream_type = stream_type.lower()
     set_file_type_metadata(stream, mi, stream_type)
     
diff --git a/src/calibre/manual/customize.rst b/src/calibre/manual/customize.rst
index 3c00787881..0efb6a3f63 100644
--- a/src/calibre/manual/customize.rst
+++ b/src/calibre/manual/customize.rst
@@ -46,7 +46,7 @@ Create a file name :file:`my_plugin.py` (the file name must end with plugin.py)
       ext  = os.path.splitext(path_to_ebook)[-1][1:].lower()
       mi = get_metadata(file, ext)
       mi.publisher = 'Hello World'
-      set_metadata(file, ext, mi)
+      set_metadata(file, mi, ext)
       return path_to_ebook
 
 That's all. To add this code to |app| as a plugin, simply create a zip file with::