diff --git a/scrapy/pipelines/images.py b/scrapy/pipelines/images.py
index a1457c7e9..add606a2e 100644
--- a/scrapy/pipelines/images.py
+++ b/scrapy/pipelines/images.py
@@ -127,7 +127,7 @@ class ImagesPipeline(FilesPipeline):
             raise ImageException("Image too small (%dx%d < %dx%d)" %
                                  (width, height, self.min_width, self.min_height))
 
-        image, buf = self.convert_image(orig_image)
+        image, buf = self.convert_image(orig_image, BytesIO(response.body))
         yield path, image, buf
 
         for thumb_id, size in six.iteritems(self.thumbs):
@@ -135,7 +135,7 @@ class ImagesPipeline(FilesPipeline):
             thumb_image, thumb_buf = self.convert_image(image, size)
             yield thumb_path, thumb_image, thumb_buf
 
-    def convert_image(self, image, size=None):
+    def convert_image(self, image, response_body, size=None):
         if image.format == 'PNG' and image.mode == 'RGBA':
             background = Image.new('RGBA', image.size, (255, 255, 255))
             background.paste(image, image)
@@ -152,6 +152,9 @@ class ImagesPipeline(FilesPipeline):
             image = image.copy()
             image.thumbnail(size, Image.ANTIALIAS)
 
+        if not size and image.format == 'JPEG':
+            return image, response_body
+
         buf = BytesIO()
         image.save(buf, 'JPEG')
         return image, buf