diff --git a/examples/wav/Makefile b/examples/wav/Makefile
index a1126f0..f2e1a2c 100644
--- a/examples/wav/Makefile
+++ b/examples/wav/Makefile
@@ -11,4 +11,4 @@ clean:
 	lame --abr 160 $<
 
 %.mp4: %.mp3
-	ffmpeg -i $< -filter_complex "[0:a]showspectrum=s=1280x720:color=intensity[v]" -map "[v]" -map 0:a $@
+	ffmpeg -i $< -filter_complex "[0:a]showspectrum=s=1280x720:color=intensity[v]" -map "[v]" -map 0:a -pix_fmt yuv420p $@