diff --git a/emmarin/cl/cl/src/crust/balance.rs b/emmarin/cl/cl/src/crust/balance.rs
index 6cd55a7..52cf97e 100644
--- a/emmarin/cl/cl/src/crust/balance.rs
+++ b/emmarin/cl/cl/src/crust/balance.rs
@@ -10,6 +10,7 @@ pub struct UnitWitness {
     pub spending_covenant: [u8; 32],
     pub minting_covenant: [u8; 32],
     pub burning_covenant: [u8; 32],
+    pub arg: [u8; 32],
 }
 
 impl UnitWitness {
@@ -19,7 +20,7 @@ impl UnitWitness {
         hasher.update(self.spending_covenant);
         hasher.update(self.minting_covenant);
         hasher.update(self.burning_covenant);
-
+        hasher.update(self.arg);
         hasher.finalize().into()
     }
 }
diff --git a/emmarin/cl/cl/tests/simple_transfer.rs b/emmarin/cl/cl/tests/simple_transfer.rs
index 81e5957..383c6c2 100644
--- a/emmarin/cl/cl/tests/simple_transfer.rs
+++ b/emmarin/cl/cl/tests/simple_transfer.rs
@@ -5,6 +5,7 @@ fn nmo_unit() -> UnitWitness {
         spending_covenant: [0; 32],
         minting_covenant: [0; 32],
         burning_covenant: [0; 32],
+        arg: [0; 32],
     }
 }
 
diff --git a/emmarin/cl/ledger/tests/simple_transfer.rs b/emmarin/cl/ledger/tests/simple_transfer.rs
index 0a2ddc4..858d8c7 100644
--- a/emmarin/cl/ledger/tests/simple_transfer.rs
+++ b/emmarin/cl/ledger/tests/simple_transfer.rs
@@ -27,6 +27,7 @@ fn nmo() -> UnitWitness {
         spending_covenant: NOP_COVENANT,
         minting_covenant: NOP_COVENANT,
         burning_covenant: NOP_COVENANT,
+        arg: [0; 32],
     }
 }