diff --git a/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.test.ts b/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.test.ts
index 3f63970d..19ad2df6 100644
--- a/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.test.ts
+++ b/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.test.ts
@@ -327,6 +327,53 @@ describe('requestSpendPermission', () => {
       });
     });
 
+    it('should return the wallet-substituted account in permission when mutableData substitution occurs', async () => {
+      const capabilities: WalletSignCapabilities = {
+        spendPermission: {
+          requireBalance: true,
+        },
+      };
+
+      // The request declares mutableData: { fields: ['message.account'] }, so the
+      // wallet is allowed to substitute account with a different (smart-wallet)
+      // address than the one originally requested.
+      const substitutedAccount = '0x00000000000000000000000000000000000000ab' as `0x${string}`;
+      const substitutedTypedData: SpendPermissionTypedData = {
+        ...mockTypedData,
+        message: {
+          ...mockTypedData.message,
+          account: substitutedAccount,
+        },
+      };
+
+      const mockWalletSignResponse = {
+        signature: mockSignature,
+        signedData: substitutedTypedData,
+      };
+
+      // createSpendPermissionTypedData returns the pre-substitution request data.
+      (createSpendPermissionTypedData as Mock).mockReturnValue(mockTypedData);
+      // The wallet returns the post-substitution signed data.
+      (mockProviderRequest as Mock).mockResolvedValue(mockWalletSignResponse);
+      (getHash as Mock).mockResolvedValue(mockPermissionHash);
+
+      const result = await requestSpendPermission({
+        ...mockRequestData,
+        capabilities,
+      });
+
+      // permissionHash is derived from the post-substitution message, ...
+      expect(getHash).toHaveBeenCalledWith({
+        permission: substitutedTypedData.message,
+        chainId: mockRequestData.chainId,
+      });
+      // ... so the returned permission must describe the same (substituted)
+      // account rather than the original pre-substitution request, otherwise
+      // permission and permissionHash describe different permissions.
+      expect(result.permission).toEqual(substitutedTypedData.message);
+      expect(result.permission.account).toBe(substitutedAccount);
+    });
+
     it('should handle invalid wallet_sign response', async () => {
       const capabilities: WalletSignCapabilities = {
         spendPermission: {
diff --git a/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.ts b/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.ts
index 850262b3..3f3da40e 100644
--- a/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.ts
+++ b/packages/account-sdk/src/interface/public-utilities/spend-permission/methods/requestSpendPermission.ts
@@ -78,6 +78,11 @@ const requestSpendPermissionFn = async (
   // Check if we should use wallet_sign (when capabilities are provided) or eth_signTypedData_v4
   let signature: string;
   let permissionHash: string;
+  // The permission message actually returned to the caller. It must match the
+  // data that permissionHash is derived from: when the wallet substitutes
+  // message.account via mutableData, this is the wallet-returned (post-
+  // substitution) message, not the original request.
+  let permissionMessage: typeof typedData.message;
 
   if (capabilities) {
     // Use wallet_sign with capabilities
@@ -126,6 +131,7 @@ const requestSpendPermissionFn = async (
       permission: signResult.signedData.message,
       chainId,
     });
+    permissionMessage = signResult.signedData.message;
   } else {
     // Use the original eth_signTypedData_v4 method
     [signature, permissionHash] = await Promise.all([
@@ -135,6 +141,7 @@ const requestSpendPermissionFn = async (
       }) as Promise<string>,
       getHash({ permission: typedData.message, chainId }),
     ]);
+    permissionMessage = typedData.message;
   }
 
   const permission: SpendPermission = {
@@ -142,7 +149,7 @@ const requestSpendPermissionFn = async (
     permissionHash,
     signature,
     chainId,
-    permission: typedData.message,
+    permission: permissionMessage,
   };
 
   return permission;