diff --git a/libavcodec/vc1.c b/libavcodec/vc1.c
index 7c4eb2e157..9b759eda1e 100644
--- a/libavcodec/vc1.c
+++ b/libavcodec/vc1.c
@@ -825,10 +825,10 @@ int vc1_parse_frame_header_adv(VC1Context *v, GetBitContext* gb)
     int scale, shift, i; /* for initializing LUT for intensity compensation */
 
     v->numref=0;
-    v->fcm=0;
-    v->field_mode=0;
     v->p_frame_skipped = 0;
     if (v->second_field) {
+        if(v->fcm!=2 || v->field_mode!=1)
+            return -1;
         v->s.pict_type = (v->fptype & 1) ? AV_PICTURE_TYPE_P : AV_PICTURE_TYPE_I;
         if (v->fptype & 4)
             v->s.pict_type = (v->fptype & 1) ? AV_PICTURE_TYPE_BI : AV_PICTURE_TYPE_B;