diff --git a/libavcodec/proresenc.c b/libavcodec/proresenc.c
index bdb826cf07..6acaededc5 100644
--- a/libavcodec/proresenc.c
+++ b/libavcodec/proresenc.c
@@ -468,7 +468,6 @@ static void put_alpha_run(PutBitContext *pb, int run)
 
 // todo alpha quantisation for high quants
 static int encode_alpha_plane(ProresContext *ctx, PutBitContext *pb,
-                              const uint16_t *src, int linesize,
                               int mbs_per_slice, uint16_t *blocks,
                               int quant)
 {
@@ -563,9 +562,8 @@ static int encode_slice(AVCodecContext *avctx, const AVFrame *pic,
             get_alpha_data(ctx, src, linesize, xp, yp,
                            pwidth, avctx->height / ctx->pictures_per_frame,
                            ctx->blocks[0], mbs_per_slice, ctx->alpha_bits);
-            sizes[i] = encode_alpha_plane(ctx, pb, src, linesize,
-                                          mbs_per_slice, ctx->blocks[0],
-                                          quant);
+            sizes[i] = encode_alpha_plane(ctx, pb, mbs_per_slice,
+                                          ctx->blocks[0], quant);
         }
         total_size += sizes[i];
     }