diff --git a/libavcodec/alacdsp.c b/libavcodec/alacdsp.c
index ecbaedb067..9996eb4319 100644
--- a/libavcodec/alacdsp.c
+++ b/libavcodec/alacdsp.c
@@ -49,7 +49,7 @@ static void append_extra_bits(int32_t *buffer[2], int32_t *extra_bits_buffer[2],
 
     for (ch = 0; ch < channels; ch++)
         for (i = 0; i < nb_samples; i++)
-            buffer[ch][i] = (buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
+            buffer[ch][i] = ((unsigned)buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
 }
 
 av_cold void ff_alacdsp_init(ALACDSPContext *c)