diff --git a/docs/src/runes/specification.md b/docs/src/runes/specification.md
index 77db3704af..d3b9b36354 100644
--- a/docs/src/runes/specification.md
+++ b/docs/src/runes/specification.md
@@ -263,6 +263,7 @@ FLAG_VALUE`:
 enum Flag {
   Etching = 0,
   Terms = 1,
+  Turbo = 2,
   Cenotaph = 127,
 }
 ```
@@ -271,6 +272,10 @@ The `Etching` flag marks this transaction as containing an etching.
 
 The `Terms` flag marks this transaction's etching as having open mint terms.
 
+The `Turbo` flag marks this transaction's etching as opting into future
+protocol changes. These protocol changes may increase light client validation
+costs, or just be highly degenerate.
+
 The `Cenotaph` flag is unrecognized.
 
 If the value of the flags field after removing recognized flags is nonzero, the