diff --git a/src/asahi/lib/decode.c b/src/asahi/lib/decode.c
index e35c535e218..6f04443de61 100644
--- a/src/asahi/lib/decode.c
+++ b/src/asahi/lib/decode.c
@@ -143,6 +143,7 @@ agxdecode_decode_segment_list(void *segment_list)
          hdr->kernel_commands_start_offset);
    fprintf(agxdecode_dump_stream, "  Kernel commands end offset: %u\n",
          hdr->kernel_commands_end_offset);
+   fprintf(agxdecode_dump_stream, "  Unknown: 0x%X\n", hdr->unk);
 
    if (hdr->padding[0] || hdr->padding[1])
       fprintf(agxdecode_dump_stream, "ERROR - padding tripped\n");
diff --git a/src/asahi/lib/io.h b/src/asahi/lib/io.h
index 35e00255e6d..582b69eab5d 100644
--- a/src/asahi/lib/io.h
+++ b/src/asahi/lib/io.h
@@ -207,7 +207,8 @@ struct agx_map_header {
    /* IOAccelSegmentListHeader */
    uint64_t cmdbuf_id; // GUID
    uint32_t segment_count;
-   uint32_t length;
+   uint16_t length;
+   uint16_t unk; // 0x8000
    uint64_t encoder_id; // GUID
 
    /* IOAccelSegmentResourceListHeader */