diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index f2b0a296b80193d012a9ff96d9fab52df85e00e6..93e9eb6ae7d69bb4dce3c7784d6d82c9977a0bf3 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -240,16 +240,17 @@ FF_ENABLE_DEPRECATION_WARNINGS
 int av_packet_add_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
                             uint8_t *data, size_t size)
 {
+    AVPacketSideData *tmp;
     int elems = pkt->side_data_elems;
 
     if ((unsigned)elems + 1 > INT_MAX / sizeof(*pkt->side_data))
         return AVERROR(ERANGE);
 
-    pkt->side_data = av_realloc(pkt->side_data,
-                                (elems + 1) * sizeof(*pkt->side_data));
-    if (!pkt->side_data)
+    tmp = av_realloc(pkt->side_data, (elems + 1) * sizeof(*tmp));
+    if (!tmp)
         return AVERROR(ENOMEM);
 
+    pkt->side_data = tmp;
     pkt->side_data[elems].data = data;
     pkt->side_data[elems].size = size;
     pkt->side_data[elems].type = type;