diff --git a/packages/account/src/BiconomySmartAccount.ts b/packages/account/src/BiconomySmartAccount.ts
index fb12a68b6..e5dba89bf 100644
--- a/packages/account/src/BiconomySmartAccount.ts
+++ b/packages/account/src/BiconomySmartAccount.ts
@@ -336,6 +336,7 @@ export class BiconomySmartAccount extends SmartAccount implements IBiconomySmart
 
     // Note: Can change the default behaviour of calling estimations using bundler/local
     userOp = await this.estimateUserOpGas({ userOp, overrides, skipBundlerGasEstimation, paymasterServiceData });
+    userOp.paymasterAndData = userOp.paymasterAndData ?? "0x";
     Logger.log("UserOp after estimation ", userOp);
 
     return userOp;
diff --git a/packages/account/src/BiconomySmartAccountV2.ts b/packages/account/src/BiconomySmartAccountV2.ts
index cc81e27b5..aec1a11fb 100644
--- a/packages/account/src/BiconomySmartAccountV2.ts
+++ b/packages/account/src/BiconomySmartAccountV2.ts
@@ -473,6 +473,7 @@ export class BiconomySmartAccountV2 extends BaseSmartAccount {
       skipBundlerGasEstimation: buildUseropDto?.skipBundlerGasEstimation,
       paymasterServiceData: buildUseropDto?.paymasterServiceData,
     });
+    userOp.paymasterAndData = userOp.paymasterAndData ?? "0x";
     Logger.log("UserOp after estimation ", userOp);
 
     return userOp;