diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 6ff9aaf361..f5eec3f2d1 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -2687,6 +2687,7 @@ static int mpeg4_update_thread_context(AVCodecContext *dst,
 {
     Mpeg4DecContext *s = dst->priv_data;
     const Mpeg4DecContext *s1 = src->priv_data;
+    int init = s->m.context_initialized;
 
     int ret = ff_mpeg_update_thread_context(dst, src);
 
@@ -2695,6 +2696,9 @@ static int mpeg4_update_thread_context(AVCodecContext *dst,
 
     memcpy(((uint8_t*)s) + sizeof(MpegEncContext), ((uint8_t*)s1) + sizeof(MpegEncContext), sizeof(Mpeg4DecContext) - sizeof(MpegEncContext));
 
+    if (CONFIG_MPEG4_DECODER && !init && s1->xvid_build >= 0)
+        ff_xvididct_init(&s->m.idsp, dst);
+
     return 0;
 }