diff --git a/src/html/document.zig b/src/html/document.zig
index 0f278f0d..11d16c3e 100644
--- a/src/html/document.zig
+++ b/src/html/document.zig
@@ -39,6 +39,8 @@ pub const HTMLDocument = struct {
     pub const prototype = *Document;
     pub const mem_guarantied = true;
 
+    pub const sub_type = "node";
+
     // JS funcs
     // --------