diff --git a/ckeditor/image/pillow_backend.py b/ckeditor/image/pillow_backend.py
index 74db2af..a888c5c 100644
--- a/ckeditor/image/pillow_backend.py
+++ b/ckeditor/image/pillow_backend.py
@@ -24,7 +24,10 @@ def image_verify(f):
 
 def create_thumbnail(file_path):
     thumbnail_filename = utils.get_thumb_filename(file_path)
-    thumbnail_format = utils.get_image_format(os.path.splitext(file_path)[1])
+    try:
+        thumbnail_format = utils.get_image_format(os.path.splitext(file_path)[1])
+    except KeyError:
+        thumbnail_format = 'image/jpeg'
     file_format = thumbnail_format.split('/')[1]
 
     image = default_storage.open(file_path)