diff --git a/src/contracts/elGamalHE.ts b/src/contracts/elGamalHE.ts
index 57416dea..0d819da0 100644
--- a/src/contracts/elGamalHE.ts
+++ b/src/contracts/elGamalHE.ts
@@ -1,4 +1,4 @@
-import { SmartContract, assert, method, prop } from 'scrypt-ts'
+import { SmartContract, assert, hash256, method, prop } from 'scrypt-ts'
 import { Point, SECP256K1 } from 'scrypt-ts-lib'
 
 export type CT = {
@@ -19,7 +19,11 @@ export class ElGamalHE extends SmartContract {
     public add(toAdd: CT) {
         // Add encrypted value to the total sum.
         this.salarySum = ElGamalHE.addCT(this.salarySum, toAdd)
-        assert(true)
+
+        const outputs =
+            this.buildStateOutput(this.ctx.utxo.value) +
+            this.buildChangeOutput()
+        assert(hash256(outputs) == this.ctx.hashOutputs, 'hashOutputs mismatch')
     }
 
     @method()
diff --git a/src/contracts/paillierHE.ts b/src/contracts/paillierHE.ts
index 9c16c725..ed98ce26 100644
--- a/src/contracts/paillierHE.ts
+++ b/src/contracts/paillierHE.ts
@@ -1,4 +1,4 @@
-import { SmartContract, assert, method, prop } from 'scrypt-ts'
+import { SmartContract, assert, hash256, method, prop } from 'scrypt-ts'
 
 export class PaillierHE extends SmartContract {
     // max # of bits for e = ceil(log2(n))
@@ -21,13 +21,21 @@ export class PaillierHE extends SmartContract {
     @method()
     public add(toAdd: bigint) {
         this.x = PaillierHE.addCT(this.x, toAdd, this.nSquare)
-        assert(true)
+
+        const outputs =
+            this.buildStateOutput(this.ctx.utxo.value) +
+            this.buildChangeOutput()
+        assert(hash256(outputs) == this.ctx.hashOutputs, 'hashOutputs mismatch')
     }
 
     @method()
     public mul(factor: bigint) {
         this.x = PaillierHE.mulCT(this.x, factor, this.nSquare)
-        assert(true)
+
+        const outputs =
+            this.buildStateOutput(this.ctx.utxo.value) +
+            this.buildChangeOutput()
+        assert(hash256(outputs) == this.ctx.hashOutputs, 'hashOutputs mismatch')
     }
 
     @method()
diff --git a/tests/paillierHE.test.ts b/tests/paillierHE.test.ts
index 26ee22b1..939276fd 100644
--- a/tests/paillierHE.test.ts
+++ b/tests/paillierHE.test.ts
@@ -27,7 +27,7 @@ describe('Heavy: Test SmartContract `PaillierHE`', () => {
         let currentInstance = instance
 
         for (let i = 0; i < 5; ++i) {
-            const nextInstance = currentInstance.next()
+            let nextInstance = currentInstance.next()
 
             // Add encrypted amount (100) to the contract commulative value.
             const toAdd = publicKey.encrypt(100n)
@@ -49,6 +49,8 @@ describe('Heavy: Test SmartContract `PaillierHE`', () => {
 
             currentInstance = nextInstance
 
+            nextInstance = currentInstance.next()
+
             // Multiply encrypted amount.
             const k = 5n
             nextInstance.x = PaillierHE.mulCT(