diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index ae50b9a2fe..3874d07000 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -529,6 +529,7 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
 
         av_freep(&h->rbsp_buffer[0]);
         av_freep(&h->rbsp_buffer[1]);
+        ff_h264_unref_picture(h, &h->last_pic_for_ec);
         memcpy(h, h1, offsetof(H264Context, intra_pcm_ptr));
         memcpy(&h->cabac, &h1->cabac,
                sizeof(H264Context) - offsetof(H264Context, cabac));