diff --git a/packages/passport/sdk/src/utils/string.test.ts b/packages/passport/sdk/src/utils/string.test.ts
index 7bf836251b..2139a13fe2 100644
--- a/packages/passport/sdk/src/utils/string.test.ts
+++ b/packages/passport/sdk/src/utils/string.test.ts
@@ -2,36 +2,36 @@ import { hexToString } from './string';
 
 describe('string', () => {
   describe('hexToString', () => {
-    it('should return hex if it is not a valid hex', () => {
+    it('should return hex if it is not a valid hex', async () => {
       const hex = '0x123';
       const hex2 = 'test';
 
-      expect(hexToString(hex)).toEqual(hex);
-      expect(hexToString(hex2)).toEqual(hex2);
+      expect(await hexToString(hex)).toEqual(hex);
+      expect(await hexToString(hex2)).toEqual(hex2);
     });
 
-    it('should return utf8 string if it is a valid utf8', () => {
+    it('should return utf8 string if it is a valid utf8', async () => {
       const hex = '0x68656c6c6f20776f726c64';
 
-      expect(hexToString(hex)).toEqual('hello world');
+      expect(await hexToString(hex)).toEqual('hello world');
     });
 
-    it('should return utf8 string if it is a valid utf8 with leading zeros', () => {
+    it('should return utf8 string if it is a valid utf8 with leading zeros', async () => {
       const hex = '0x0068656c6c6f20776f726c64'; // 'hello world' with leading zero
 
-      expect(hexToString(hex)).toEqual('hello world');
+      expect(await hexToString(hex)).toEqual('hello world');
     });
 
-    it('should return empty string if input is an empty string', () => {
+    it('should return empty string if input is an empty string', async () => {
       const hex = '';
 
-      expect(hexToString(hex)).toEqual('');
+      expect(await hexToString(hex)).toEqual('');
     });
 
-    it('should return hex if it is a valid hex but not a valid utf8', () => {
+    it('should return hex if it is a valid hex but not a valid utf8', async () => {
       const hex = '0x1234567890abcdef'; // valid hex but not a valid utf8
 
-      expect(hexToString(hex)).toEqual(hex);
+      expect(await hexToString(hex)).toEqual(hex);
     });
   });
 });
diff --git a/packages/passport/sdk/src/utils/string.ts b/packages/passport/sdk/src/utils/string.ts
index 499f2e109e..15a15acf48 100644
--- a/packages/passport/sdk/src/utils/string.ts
+++ b/packages/passport/sdk/src/utils/string.ts
@@ -1,9 +1,15 @@
 import { utils } from 'ethers';
 
-export const hexToString = (hex: string) => {
+export const hexToString = async (hex: string) => {
   if (!hex) return hex;
 
   try {
+    if (typeof window !== 'undefined' && !window.Buffer) {
+      // Use dynamic import to load Buffer
+      const bufferModule = await import('buffer');
+      window.Buffer = bufferModule.Buffer;
+    }
+
     const stripped = utils.stripZeros(utils.arrayify(hex));
     const buff = Buffer.from(stripped);
     return buff.length === 32 ? hex : utils.toUtf8String(stripped);
diff --git a/packages/passport/sdk/src/zkEvm/personalSign.ts b/packages/passport/sdk/src/zkEvm/personalSign.ts
index 53e90f9d96..369ad2b742 100644
--- a/packages/passport/sdk/src/zkEvm/personalSign.ts
+++ b/packages/passport/sdk/src/zkEvm/personalSign.ts
@@ -38,13 +38,7 @@ export const personalSign = async ({
     throw new JsonRpcError(RpcErrorCode.INVALID_PARAMS, 'personal_sign requires the signer to be the from address');
   }
 
-  if (typeof window !== 'undefined' && !window.Buffer) {
-    // Use dynamic import to load Buffer
-    const bufferModule = await import('buffer');
-    window.Buffer = bufferModule.Buffer;
-  }
-
-  const payload = hexToString(message);
+  const payload = await hexToString(message);
   const { chainId } = await rpcProvider.detectNetwork();
   flow.addEvent('endDetectNetwork');
   const chainIdBigNumber = BigNumber.from(chainId);