diff --git a/test/unit/attesters/hydra-s1/hydra-s1-accountbound-attester.test.ts b/test/unit/attesters/hydra-s1/hydra-s1-accountbound-attester.test.ts
index 616f070..d303900 100644
--- a/test/unit/attesters/hydra-s1/hydra-s1-accountbound-attester.test.ts
+++ b/test/unit/attesters/hydra-s1/hydra-s1-accountbound-attester.test.ts
@@ -253,9 +253,12 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
       expect(buildAttestations[0].issuer).to.eql(hydraS1AccountboundAttester.address);
       expect(buildAttestations[0].value.toNumber()).to.eql(sourceValue.toNumber());
       expect(buildAttestations[0].timestamp).to.eql(group.properties.generationTimestamp);
-      expect(
-        utils.defaultAbiCoder.decode(['bytes', 'uint16'], buildAttestations[0].extraData)
-      ).to.eql([BigNumber.from(inputs.publicInputs.nullifier)._hex, 0]);
+      expect(buildAttestations[0].extraData).to.eql(
+        encodeAccountBoundAttestationExtraData({
+          nullifier: inputs.publicInputs.nullifier,
+          burnCount: 0,
+        })
+      );
     });
   });
 
@@ -562,13 +565,6 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
       const generateAttestationsTransaction =
         await hydraS1AccountboundAttester.generateAttestations(request, proof.toBytes());
 
-      const attestationsExtraData = await attestationsRegistry.getAttestationExtraData(
-        (
-          await hydraS1AccountboundAttester.AUTHORIZED_COLLECTION_ID_FIRST()
-        ).add(group.properties.groupIndex),
-        request.destination
-      );
-
       // 0 - Checks that the transaction emitted the event
       await expect(generateAttestationsTransaction)
         .to.emit(hydraS1AccountboundAttester, 'AttestationGenerated')
@@ -580,7 +576,10 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
           hydraS1AccountboundAttester.address,
           sourceValue,
           group.properties.generationTimestamp,
-          attestationsExtraData,
+          encodeAccountBoundAttestationExtraData({
+            nullifier: inputs.publicInputs.nullifier,
+            burnCount: 0,
+          }),
         ]);
 
       // 1 - Checks that the provided nullifier was successfully recorded in the attester
@@ -621,12 +620,12 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
         destinationSigner.address
       );
 
-      // expect(attestationExtraData).to.be.eql(
-      //   encodeAccountBoundAttestationExtraData({
-      //     nullifier: inputs.publicInputs.nullifier,
-      //     burnCount: 0,
-      //   })
-      // );
+      expect(attestationExtraData).to.be.eql(
+        encodeAccountBoundAttestationExtraData({
+          nullifier: inputs.publicInputs.nullifier,
+          burnCount: 0,
+        })
+      );
 
       expect(
         await hydraS1AccountboundAttester.getNullifierFromExtraData(
@@ -686,14 +685,6 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
       const generateAttestationsTransaction =
         await hydraS1AccountboundAttester.generateAttestations(newRequest, newProof.toBytes());
 
-      // burnCount should be recorded in the attestationsRegistry
-      const attestationsExtraData = await attestationsRegistry.getAttestationExtraData(
-        (
-          await hydraS1AccountboundAttester.AUTHORIZED_COLLECTION_ID_FIRST()
-        ).add(group.properties.groupIndex),
-        newRequest.destination
-      );
-
       // 0 - Checks that the transaction emitted the event
       await expect(generateAttestationsTransaction)
         .to.emit(hydraS1AccountboundAttester, 'AttestationGenerated')
@@ -705,7 +696,10 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
           hydraS1AccountboundAttester.address,
           sourceValue,
           group.properties.generationTimestamp,
-          attestationsExtraData,
+          encodeAccountBoundAttestationExtraData({
+            nullifier: inputs.publicInputs.nullifier,
+            burnCount: 1, // burn count should be incremented
+          }),
         ]);
       await expect(generateAttestationsTransaction)
         .to.emit(hydraS1AccountboundAttester, 'NullifierDestinationUpdated')
@@ -733,10 +727,20 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
         )
       ).to.be.eql(1); // the burnCount should be incremented
 
-      expect(utils.defaultAbiCoder.decode(['bytes', 'uint16'], attestationsExtraData)).to.eql([
-        BigNumber.from(inputs.publicInputs.nullifier)._hex,
-        1,
-      ]);
+      // burnCount should be recorded in the attestationsRegistry
+      expect(
+        await attestationsRegistry.getAttestationExtraData(
+          (
+            await hydraS1AccountboundAttester.AUTHORIZED_COLLECTION_ID_FIRST()
+          ).add(group.properties.groupIndex),
+          destination2Signer.address
+        )
+      ).to.equal(
+        encodeAccountBoundAttestationExtraData({
+          nullifier: inputs.publicInputs.nullifier,
+          burnCount: 1, // burnCount should be incremented
+        })
+      );
       // 2 - Checks that the attester unrecorded & rerecorded the attestation in the registry
       // 2.1 - Checks that the old destination has not anymore it's attestation
       expect(
@@ -821,13 +825,6 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
       const generateAttestationsTransaction =
         await hydraS1AccountboundAttester.generateAttestations(renewRequest, renewProof.toBytes());
 
-      const attestationsExtraData = await attestationsRegistry.getAttestationExtraData(
-        (
-          await hydraS1AccountboundAttester.AUTHORIZED_COLLECTION_ID_FIRST()
-        ).add(group.properties.groupIndex),
-        renewRequest.destination
-      );
-
       // 0 - Checks that the transaction emitted the event with the new timestamp
       await expect(generateAttestationsTransaction)
         .to.emit(hydraS1AccountboundAttester, 'AttestationGenerated')
@@ -839,7 +836,10 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
           hydraS1AccountboundAttester.address,
           sourceValue,
           renewGenerationTimestamp,
-          attestationsExtraData,
+          encodeAccountBoundAttestationExtraData({
+            nullifier: inputs.publicInputs.nullifier,
+            burnCount: 1,
+          }),
         ]);
 
       // A renew should not have changed the nullifierData
@@ -912,13 +912,6 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
       const generateAttestationsTransaction =
         await hydraS1AccountboundAttester.generateAttestations(renewRequest, renewProof.toBytes());
 
-      const attestationsExtraData = await attestationsRegistry.getAttestationExtraData(
-        (
-          await hydraS1AccountboundAttester.AUTHORIZED_COLLECTION_ID_FIRST()
-        ).add(group.properties.groupIndex),
-        renewRequest.destination
-      );
-
       // Checks that the transaction emitted the event with a claimedValue of zero
       await expect(generateAttestationsTransaction)
         .to.emit(hydraS1AccountboundAttester, 'AttestationGenerated')
@@ -930,7 +923,10 @@ describe('Test HydraS1 Accountbound Attester contract', () => {
           hydraS1AccountboundAttester.address,
           0, // claimedValue
           group.properties.generationTimestamp,
-          attestationsExtraData,
+          encodeAccountBoundAttestationExtraData({
+            nullifier: inputs.publicInputs.nullifier,
+            burnCount: 1,
+          }),
         ]);
 
       //  Checks that the attestation in the registry has a value of zero
diff --git a/test/utils/hydra-s1-accountbound.ts b/test/utils/hydra-s1-accountbound.ts
index e59166d..65250a6 100644
--- a/test/utils/hydra-s1-accountbound.ts
+++ b/test/utils/hydra-s1-accountbound.ts
@@ -121,5 +121,8 @@ export const encodeAccountBoundAttestationExtraData = ({
   nullifier: BigNumberish | BigInt;
   burnCount: number;
 }) => {
-  return ethers.utils.solidityPack(['uint256', 'uint16'], [nullifier, burnCount]);
+  return ethers.utils.defaultAbiCoder.encode(
+    ['bytes', 'uint16'],
+    [ethers.utils.defaultAbiCoder.encode(['uint256'], [nullifier]), burnCount]
+  );
 };