diff --git a/src/calibre/ebooks/oeb/polish/main.py b/src/calibre/ebooks/oeb/polish/main.py
index 7ec34b5174..08b5004c91 100644
--- a/src/calibre/ebooks/oeb/polish/main.py
+++ b/src/calibre/ebooks/oeb/polish/main.py
@@ -175,7 +175,7 @@ def gui_polish(data):
     if not data.pop('metadata'):
         data.pop('opf')
     if not data.pop('do_cover'):
-        data.pop('cover')
+        data.pop('cover', None)
     file_map = {x:x for x in files}
     opts = ALL_OPTS.copy()
     opts.update(data)