diff --git a/src/calibre/gui2/dnd.py b/src/calibre/gui2/dnd.py
index 980bd021ec..6ead535d45 100644
--- a/src/calibre/gui2/dnd.py
+++ b/src/calibre/gui2/dnd.py
@@ -24,7 +24,7 @@ from polyglot.queue import Queue, Empty
 
 def image_extensions():
     if not hasattr(image_extensions, 'ans'):
-        image_extensions.ans = [as_unicode_polyglot(x) for x in QImageReader.supportedImageFormats()]
+        image_extensions.ans = [x.data().decode('utf-8') for x in QImageReader.supportedImageFormats()]
     return image_extensions.ans
 
 
diff --git a/src/calibre/gui2/tweak_book/editor/canvas.py b/src/calibre/gui2/tweak_book/editor/canvas.py
index 0aade16f18..01073042bc 100644
--- a/src/calibre/gui2/tweak_book/editor/canvas.py
+++ b/src/calibre/gui2/tweak_book/editor/canvas.py
@@ -24,7 +24,6 @@ from calibre.utils.img import (
     remove_borders_from_image, gaussian_sharpen_image, gaussian_blur_image, image_to_data, despeckle_image,
     normalize_image, oil_paint_image
 )
-from polyglot.builtins import as_unicode
 
 
 def painter(func):
@@ -325,7 +324,7 @@ class Canvas(QWidget):
         if not self.is_modified:
             return self.original_image_data
         fmt = self.original_image_format or 'JPEG'
-        if fmt.lower() not in set(map(as_unicode, QImageWriter.supportedImageFormats())):
+        if fmt.lower() not in {x.data().decode('utf-8') for x in QImageWriter.supportedImageFormats()}:
             if fmt.lower() == 'gif':
                 data = image_to_data(self.current_image, fmt='PNG', png_compression_level=0)
                 from PIL import Image