diff --git a/src/calibre/customize/conversion.py b/src/calibre/customize/conversion.py
index 05dc02404a..aa2dd48b9e 100644
--- a/src/calibre/customize/conversion.py
+++ b/src/calibre/customize/conversion.py
@@ -350,7 +350,7 @@ class OutputFormatPlugin(Plugin):
 
     def specialize_css_for_output(self, log, opts, item, stylizer):
         '''
-        Can be used to make changes to the css during the CSS flattening
+        Can be used to make changes to the CSS during the CSS flattening
         process.
 
         :param item: The item (HTML file) being processed