diff --git a/backend/open_webui/routers/images.py b/backend/open_webui/routers/images.py
index 8c6e772896..c894f2c651 100644
--- a/backend/open_webui/routers/images.py
+++ b/backend/open_webui/routers/images.py
@@ -509,8 +509,9 @@ async def get_image_data(data: str, headers=None, trusted_base_url: str | None =
                 mime_type = header.split(';')[0].lstrip('data:')
                 img_data = base64.b64decode(encoded)
             else:
-                mime_type = 'image/png'
                 img_data = base64.b64decode(data)
+                with Image.open(io.BytesIO(img_data)) as image:
+                    mime_type = Image.MIME.get(image.format, 'image/png')
             return img_data, mime_type
     except Exception as e:
         log.exception(f'Error loading image data: {e}')
@@ -520,7 +521,7 @@ async def get_image_data(data: str, headers=None, trusted_base_url: str | None =
 async def upload_image(request, image_data, content_type, metadata, user, db=None):
     if image_data is None or content_type is None:
         raise ValueError('Failed to retrieve image data from the generation backend')
-    image_format = mimetypes.guess_extension(content_type)
+    image_format = IMAGE_FILE_EXTENSIONS.get(content_type.lower()) or mimetypes.guess_extension(content_type) or '.png'
     file = UploadFile(
         file=io.BytesIO(image_data),
         filename=f'generated-image{image_format}',  # will be converted to a unique ID on upload_file