| Index: source/libvpx/vp9/decoder/vp9_decodeframe.c | 
| =================================================================== | 
| --- source/libvpx/vp9/decoder/vp9_decodeframe.c	(revision 278870) | 
| +++ source/libvpx/vp9/decoder/vp9_decodeframe.c	(working copy) | 
| @@ -1077,7 +1077,7 @@ | 
| // Show an existing frame directly. | 
| const int frame_to_show = cm->ref_frame_map[vp9_rb_read_literal(rb, 3)]; | 
|  | 
| -    if (cm->frame_bufs[frame_to_show].ref_count < 1) | 
| +    if (frame_to_show < 0 || cm->frame_bufs[frame_to_show].ref_count < 1) | 
| vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM, | 
| "Buffer %d does not contain a decoded frame", | 
| frame_to_show); | 
|  |