diff --git a/vpxdec.c b/vpxdec.c
index 5eb0bebde659e655c954aa2d913d98b5c8c74765..dd1796380a77dfdc4f3c68a7d2b6152acd6db5c3 100644
--- a/vpxdec.c
+++ b/vpxdec.c
@@ -442,6 +442,8 @@ unsigned int file_is_raw(FILE *infile,
     int is_raw = 0;
     vpx_codec_stream_info_t si;
 
+    si.sz = sizeof(si);
+
     if (fread(buf, 1, 32, infile) == 32)
     {
         int i;