diff --git a/libavcodec/alacenc.c b/libavcodec/alacenc.c
index bb618e16f2..235bff6637 100644
--- a/libavcodec/alacenc.c
+++ b/libavcodec/alacenc.c
@@ -257,7 +257,7 @@ static void alac_linear_predictor(AlacEncodeContext *s, int ch)
         // generate warm-up samples
         residual[0] = samples[0];
         for(i=1;i<=lpc.lpc_order;i++)
-            residual[i] = samples[i] - samples[i-1];
+            residual[i] = sign_extend(samples[i] - samples[i-1], s->write_sample_size);
 
         // perform lpc on remaining samples
         for(i = lpc.lpc_order + 1; i < s->avctx->frame_size; i++) {