diff --git a/src/Manticore.php b/src/Manticore.php
index f4d7246..4f19371 100644
--- a/src/Manticore.php
+++ b/src/Manticore.php
@@ -17,7 +17,8 @@ class Manticore
     private const OP_KEVA_DELETE    = 3;
     private const OP_HASH160        = 4;
     private const OP_RETURN         = 5;
-    private const OP_NOP            = 6;
+    private const OP_DUP            = 6;
+    private const OP_NOP            = 7;
 
     public function __construct(
         ?string $name = 'kvazar',
@@ -170,6 +171,9 @@ class Manticore
             case 'OP_RETURN':
                 return self::OP_RETURN;
 
+            case 'OP_DUP':
+                return self::OP_DUP;
+
             case 'OP_NOP':
                 return self::OP_NOP;