diff --git a/docs/reference/ImageSequence.rst b/docs/reference/ImageSequence.rst
index 85539cb9e..f8ea9ee92 100644
--- a/docs/reference/ImageSequence.rst
+++ b/docs/reference/ImageSequence.rst
@@ -19,7 +19,7 @@ Extracting frames from an animation
     index = 1
     for frame in ImageSequence.Iterator(im):
         frame.save("frame%d.png" % index)
-        index = index + 1
+        index += 1
 
 The :py:class:`~PIL.ImageSequence.Iterator` class
 -------------------------------------------------