diff --git a/src/envelope.rs b/src/envelope.rs
index 65fc93b049..ed712afe61 100644
--- a/src/envelope.rs
+++ b/src/envelope.rs
@@ -14,8 +14,11 @@ use {
 pub(crate) const PROTOCOL_ID: [u8; 3] = *b"ord";
 
 pub(crate) const BODY_TAG: [u8; 0] = [];
-pub(crate) const CONTENT_TYPE_TAG: [u8; 1] = [1];
 pub(crate) const POINTER_TAG: [u8; 1] = [2];
+#[allow(unused)]
+pub(crate) const UNBOUND_TAG: [u8; 1] = [66];
+
+pub(crate) const CONTENT_TYPE_TAG: [u8; 1] = [1];
 pub(crate) const PARENT_TAG: [u8; 1] = [3];
 pub(crate) const METADATA_TAG: [u8; 1] = [5];
 pub(crate) const METAPROTOCOL_TAG: [u8; 1] = [7];
@@ -834,6 +837,20 @@ mod tests {
     );
   }
 
+  #[test]
+  fn tag_66_makes_inscriptions_unbound() {
+    assert_eq!(
+      parse(&[envelope(&[b"ord", &UNBOUND_TAG, &[1]])]),
+      vec![ParsedEnvelope {
+        payload: Inscription {
+          unrecognized_even_field: true,
+          ..Default::default()
+        },
+        ..Default::default()
+      }],
+    );
+  }
+
   #[test]
   fn incomplete_field() {
     assert_eq!(