diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index 9bfb66b04c..6f9168f06f 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -1322,7 +1322,7 @@ int MPV_encode_init(AVCodecContext *avctx)
     if(s->modified_quant)
         s->chroma_qscale_table= ff_h263_chroma_qscale_table;
     s->progressive_frame=
-    s->progressive_sequence= !(avctx->flags & (CODEC_FLAG_INTERLACED_DCT|CODEC_FLAG_INTERLACED_ME));
+    s->progressive_sequence= !(avctx->flags & (CODEC_FLAG_INTERLACED_DCT|CODEC_FLAG_INTERLACED_ME|CODEC_FLAG_ALT_SCAN));
     s->quant_precision=5;
 
     ff_set_cmp(&s->dsp, s->dsp.ildct_cmp, s->avctx->ildct_cmp);