diff --git a/libavcodec/libmp3lame.c b/libavcodec/libmp3lame.c
index 3e8d92a3a5..f3c4528c07 100644
--- a/libavcodec/libmp3lame.c
+++ b/libavcodec/libmp3lame.c
@@ -169,7 +169,7 @@ static int MP3lame_encode_frame(AVCodecContext *avctx, unsigned char *frame,
         }
     } else {
         lame_result = lame_encode_flush(s->gfp, s->buffer + s->buffer_index,
-                                        s->buffer_size - s->buffer_index);
+                                        BUFFER_SIZE - s->buffer_index);
     }
 
     if (lame_result < 0) {