diff --git a/src/feeBumpBuilder.ts b/src/feeBumpBuilder.ts
index 215d8ed..dbf1ba8 100644
--- a/src/feeBumpBuilder.ts
+++ b/src/feeBumpBuilder.ts
@@ -12,6 +12,7 @@ import {
   TransactionBuilder,
   xdr,
   FeeBumpTransaction,
+  Keypair,
 } from "@stellar/stellar-sdk";
 import { InvalidTransactionTypeError } from "./errors.js";
 import { checkPayerReadiness } from "./preflightChecker.js";
@@ -70,7 +71,7 @@ export function buildFeeBump(
 
   // Build the fee bump from the inner transaction
   const feeBumpTx = TransactionBuilder.buildFeeBumpTransaction(
-    feeSource,
+    Keypair.fromPublicKey(feeSource),
     effectiveFee,
     innerTx,
     networkPassphrase,
diff --git a/test/feeBumpBuilder.test.ts b/test/feeBumpBuilder.test.ts
index cc3fd5a..682bffd 100644
--- a/test/feeBumpBuilder.test.ts
+++ b/test/feeBumpBuilder.test.ts
@@ -29,6 +29,7 @@ describe("buildFeeBump", () => {
     const feeBumpTx = buildFeeBump(innerTx, feeSource, BASE_FEE, networkPassphrase);
 
     expect(feeBumpTx).toBeDefined();
+    expect(feeBumpTx.feeSource).toBe(feeSource);
     const xdr = feeBumpToXDR(feeBumpTx);
     expect(xdr).toBeTruthy();
     expect(typeof xdr).toBe("string");
@@ -62,6 +63,7 @@ describe("buildFeeBump", () => {
     const feeBumpTx = buildFeeBump(innerTx, feeSource, BASE_FEE, networkPassphrase);
 
     const xdr = feeBumpToXDR(feeBumpTx);
+    expect(feeBumpTx.feeSource).toBe(feeSource);
     expect(xdr).toBeTruthy();
 
     // Verify the inner transaction is accessible in the fee bump