diff --git a/src/calibre/gui2/convert/bulk.py b/src/calibre/gui2/convert/bulk.py
index 57fe421a17..bbd3d685ee 100644
--- a/src/calibre/gui2/convert/bulk.py
+++ b/src/calibre/gui2/convert/bulk.py
@@ -125,8 +125,7 @@ class BulkConfig(Config):
             preferred_output_format and preferred_output_format \
             in output_formats else sort_formats_by_preference(output_formats,
                     [prefs['output_format']])[0]
-        self.output_formats.addItems(list(map(unicode_type, [x.upper() for x in
-            output_formats])))
+        self.output_formats.addItems((unicode_type(x.upper()) for x in output_formats))
         self.output_formats.setCurrentIndex(output_formats.index(preferred_output_format))
 
     def accept(self):
diff --git a/src/calibre/gui2/convert/single.py b/src/calibre/gui2/convert/single.py
index c3db4fff35..3efe17ca1e 100644
--- a/src/calibre/gui2/convert/single.py
+++ b/src/calibre/gui2/convert/single.py
@@ -284,10 +284,8 @@ class Config(QDialog):
             preferred_output_format in output_formats else \
             sort_formats_by_preference(output_formats,
                     [prefs['output_format']])[0]
-        self.input_formats.addItems(list(map(unicode_type, [x.upper() for x in
-            input_formats])))
-        self.output_formats.addItems(list(map(unicode_type, [x.upper() for x in
-            output_formats])))
+        self.input_formats.addItems((unicode_type(x.upper()) for x in input_formats))
+        self.output_formats.addItems((unicode_type(x.upper()) for x in output_formats))
         self.input_formats.setCurrentIndex(input_formats.index(input_format))
         self.output_formats.setCurrentIndex(output_formats.index(preferred_output_format))