diff --git a/src/filter/plugins/FfmpegFilter.cxx b/src/filter/plugins/FfmpegFilter.cxx
index 0bdae78e2..af90b795a 100644
--- a/src/filter/plugins/FfmpegFilter.cxx
+++ b/src/filter/plugins/FfmpegFilter.cxx
@@ -57,7 +57,6 @@ FfmpegFilter::FilterPCM(ConstBuffer<void> src)
 	in_frame->nb_samples = src.size / in_audio_frame_size;
 
 	in_frame.GetBuffer();
-	in_frame.MakeWritable();
 
 	memcpy(in_frame.GetData(0), src.data, src.size);