diff --git a/utilities/wallet-tester/src/common/components/TxBuilder.tsx b/utilities/wallet-tester/src/common/components/TxBuilder.tsx
index 3f06a0d9f7..fe29b8f31b 100644
--- a/utilities/wallet-tester/src/common/components/TxBuilder.tsx
+++ b/utilities/wallet-tester/src/common/components/TxBuilder.tsx
@@ -354,9 +354,10 @@ function TxBuilder({ utxos, addresses, onSubmit: onPropSubmit = noop }: Props) {
         onRemoveClick={() => resetField("networkId")}
         render={() => (
           <Input
-            type="text"
-            disabled={true}
-            placeholder="Auto generated"
+            type="number"
+            min={0}
+            max={1}
+            placeholder="0: testnet, 1: mainnet"
             label="Network ID"
             formRegister={register("networkId")}
           />
diff --git a/utilities/wallet-tester/src/common/helpers/buildUnsignedTx.ts b/utilities/wallet-tester/src/common/helpers/buildUnsignedTx.ts
index 420b2aa823..e6da7201fc 100644
--- a/utilities/wallet-tester/src/common/helpers/buildUnsignedTx.ts
+++ b/utilities/wallet-tester/src/common/helpers/buildUnsignedTx.ts
@@ -11,6 +11,7 @@ import {
   GeneralTransactionMetadata,
   Int,
   LinearFee,
+  NetworkId,
   RewardAddress,
   StakeCredential,
   StakeDelegation,
@@ -173,8 +174,7 @@ export default async function buildUnsignedTx(
 
   // #15 add network id
   if (builder.networkId) {
-    txBuilder.add_change_if_needed
-    // note: auto generated
+    // note: network id will be after build the transaction builder
   }
 
   // aux data
@@ -223,7 +223,15 @@ export default async function buildUnsignedTx(
   }
 
   // build a full transaction, passing in empty witness set
-  const unsignedTx = Transaction.new(txBuilder.build(), TransactionWitnessSet.new(), auxMetadata);
+  const txBody = txBuilder.build();
+  
+  // set network id after build
+  if (builder.networkId && [0, 1].includes(Number(builder.networkId))) {
+    const networkId = Number(builder.networkId) === 0 ? NetworkId.testnet() : NetworkId.mainnet()
+    txBody.set_network_id(networkId);
+  }
+
+  const unsignedTx = Transaction.new(txBody, TransactionWitnessSet.new(), auxMetadata);
 
   return unsignedTx;
 }