diff --git a/src/calibre/gui2/convert/bulk.py b/src/calibre/gui2/convert/bulk.py
index 91efc73ca9..8c1ef8cb96 100644
--- a/src/calibre/gui2/convert/bulk.py
+++ b/src/calibre/gui2/convert/bulk.py
@@ -119,7 +119,7 @@ class BulkConfig(Config):
 
     def setup_output_formats(self, db, preferred_output_format):
         if preferred_output_format:
-            preferred_output_format = preferred_output_format.lower()
+            preferred_output_format = preferred_output_format.upper()
         output_formats = get_output_formats(preferred_output_format)
         preferred_output_format = preferred_output_format if \
             preferred_output_format and preferred_output_format \
diff --git a/src/calibre/gui2/convert/single.py b/src/calibre/gui2/convert/single.py
index e8342610dd..945ed42594 100644
--- a/src/calibre/gui2/convert/single.py
+++ b/src/calibre/gui2/convert/single.py
@@ -252,7 +252,7 @@ class Config(ResizableDialog, Ui_Dialog):
     def setup_input_output_formats(self, db, book_id, preferred_input_format,
             preferred_output_format):
         if preferred_output_format:
-            preferred_output_format = preferred_output_format.lower()
+            preferred_output_format = preferred_output_format.upper()
         output_formats = get_output_formats(preferred_output_format)
         input_format, input_formats = get_input_format_for_book(db, book_id,
                 preferred_input_format)