diff --git a/src/asahi/genxml/cmdbuf.xml b/src/asahi/genxml/cmdbuf.xml
index d937477b8b2..7496c60e050 100644
--- a/src/asahi/genxml/cmdbuf.xml
+++ b/src/asahi/genxml/cmdbuf.xml
@@ -938,8 +938,7 @@
     <field name="Instance stride present" size="1" start="25" type="bool"/>
 
     <field name="Indirect present" size="1" start="26" type="bool"/>
-    <!-- Present for both indirect and direct -->
-    <field name="Unknown present" size="1" start="28" type="bool"/>
+    <field name="Factor buffer size present" size="1" start="28" type="bool"/>
 
     <field name="Unknown 1" size="1" start="28" type="hex"/> <!-- 1 -->
     <field name="Block Type" size="3" start="29" type="VDM Block Type" default="Tessellate"/>
@@ -979,8 +978,8 @@
     <field name="Size" size="32" start="2:0" type="uint"/>
   </struct>
 
-  <struct name="VDM Tessellate: Unknown" size="4">
-    <field name="Unknown 7" size="32" start="0" type="hex"/> <!-- 3F -->
+  <struct name="VDM Tessellate: Factor buffer size" size="4">
+    <field name="Size (words)" size="32" start="0" type="uint" modifier="minus(1)"/>
   </struct>
 
   <struct name="VDM Stream Terminate" size="32">
diff --git a/src/asahi/lib/decode.c b/src/asahi/lib/decode.c
index 417f6d865c6..a09900f8e76 100644
--- a/src/asahi/lib/decode.c
+++ b/src/asahi/lib/decode.c
@@ -725,7 +725,7 @@ agxdecode_vdm(struct agxdecode_ctx *ctx, const uint8_t *map, uint64_t *link,
       TESS_PRINT(base_instance, BASE_INSTANCE, "Base instance");
       TESS_PRINT(instance_stride, INSTANCE_STRIDE, "Instance stride");
       TESS_PRINT(indirect, INDIRECT, "Indirect");
-      TESS_PRINT(unknown, UNKNOWN, "Unknown");
+      TESS_PRINT(factor_buffer_size, FACTOR_BUFFER_SIZE, "Factor buffer size");
 
 #undef TESS_PRINT
       return length;