diff --git a/libavcodec/mpeg12.c b/libavcodec/mpeg12.c
index e818bbcd12935689ab0f6e1467af1a7a75460708..8871769a3bec10ef61c2d505c5a17d5317e7ab27 100644
--- a/libavcodec/mpeg12.c
+++ b/libavcodec/mpeg12.c
@@ -2304,6 +2304,9 @@ static int mpeg_decode_frame(AVCodecContext *avctx,
                     mpeg_decode_user_data(avctx, 
                                           buf_ptr, input_size);
                     break;
+                case GOP_START_CODE:
+                    s2->first_field=0;
+                    break;
                 default:
                     if (start_code >= SLICE_MIN_START_CODE &&
                         start_code <= SLICE_MAX_START_CODE) {