diff --git a/src/calibre/ebooks/mobi/reader/mobi6.py b/src/calibre/ebooks/mobi/reader/mobi6.py
index 0daab71749..d817d58b21 100644
--- a/src/calibre/ebooks/mobi/reader/mobi6.py
+++ b/src/calibre/ebooks/mobi/reader/mobi6.py
@@ -916,6 +916,7 @@ class MobiReader:
                 except AnimatedGIF:
                     pass
                 except OSError:
+                    self.log.warn(f'Ignoring undecodeable GIF image at index {image_index}')
                     continue
             path = os.path.join(output_dir, '%05d.%s' % (image_index, imgfmt))
             image_name_map[image_index] = os.path.basename(path)