diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index d582e8f96c..e350f0169c 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -980,7 +980,7 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
 
         ff_mpeg_er_frame_start(s);
 
-        v->bits = buf_size * 8;
+        v->bits = FFMIN(buf_size * 8, s->gb.size_in_bits);
         v->end_mb_x = s->mb_width;
         if (v->field_mode) {
             s->current_picture.f->linesize[0] <<= 1;
@@ -1052,8 +1052,10 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
                 continue;
             }
             ff_vc1_decode_blocks(v);
-            if (i != n_slices)
+            if (i != n_slices) {
                 s->gb = slices[i].gb;
+                v->bits = FFMIN(buf_size * 8, s->gb.size_in_bits);
+            }
         }
         if (v->field_mode) {
             v->second_field = 0;