diff --git a/README.md b/README.md
index 84a0f56..fbf17da 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ Flip a video horizontally:
 import ffmpeg
 stream = ffmpeg.input('input.mp4')
 stream = ffmpeg.hflip(stream)
-stream = ffmpeg.output(stream)
+stream = ffmpeg.output(stream, 'output.mp4')
 ffmpeg.run(v)
 ```