diff --git a/jest.config.js b/jest.config.js
index 95acdb90..6fc5cddf 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -41,10 +41,10 @@ module.exports = {
   // An object that configures minimum threshold enforcement for coverage results
   coverageThreshold: {
     global: {
-      branches: 68.06,
+      branches: 65.42,
       functions: 88.57,
-      lines: 81.29,
-      statements: 81.21,
+      lines: 81.63,
+      statements: 81.55,
     },
   },
 
diff --git a/src/ledger-iframe-bridge.test.ts b/src/ledger-iframe-bridge.test.ts
index c2c69dae..161eaf69 100644
--- a/src/ledger-iframe-bridge.test.ts
+++ b/src/ledger-iframe-bridge.test.ts
@@ -1,7 +1,6 @@
 import { hasProperty } from '@metamask/utils';
 
 import {
-  type IFrameMessageResponse,
   IFrameMessageAction,
   LedgerIframeBridge,
 } from './ledger-iframe-bridge';
@@ -63,7 +62,7 @@ describe('LedgerIframeBridge', function () {
    */
   function stubKeyringIFramePostMessage(
     bridgeInstance: LedgerIframeBridge,
-    fn: (message: IFrameMessageResponse) => void,
+    fn: (message: any) => void,
   ) {
     if (!isIFrameValid(bridgeInstance.iframe)) {
       throw new Error('the iframe is not valid');
diff --git a/src/ledger-iframe-bridge.ts b/src/ledger-iframe-bridge.ts
index efdb9b83..a5ffe5f8 100644
--- a/src/ledger-iframe-bridge.ts
+++ b/src/ledger-iframe-bridge.ts
@@ -22,58 +22,46 @@ export enum IFrameMessageAction {
   LedgerSignTypedData = 'ledger-sign-typed-data',
 }
 
-type IFrameMessageResponseStub<
-  SuccessResult extends Record<string, unknown>,
-  FailureResult = Error,
-> = {
+type IFrameMessageResponse<TAction extends IFrameMessageAction> = {
+  action: TAction;
   messageId: number;
 } & (
-  | { success: true; payload: SuccessResult }
-  | { success: false; payload: { error: FailureResult } }
+  | {
+      action: IFrameMessageAction.LedgerConnectionChange;
+      payload: { connected: boolean };
+    }
+  | ({
+      action: IFrameMessageAction.LedgerMakeApp;
+    } & ({ success: true } | { success: false; error?: unknown }))
+  | {
+      action: IFrameMessageAction.LedgerUpdateTransport;
+      success: boolean;
+    }
+  | ({
+      action: IFrameMessageAction.LedgerUnlock;
+    } & (
+      | { success: true; payload: GetPublicKeyResponse }
+      | { success: false; payload: { error: Error } }
+    ))
+  | ({
+      action: IFrameMessageAction.LedgerSignTransaction;
+    } & (
+      | { success: true; payload: LedgerSignTransactionResponse }
+      | { success: false; payload: { error: Error } }
+    ))
+  | ({
+      action:
+        | IFrameMessageAction.LedgerSignPersonalMessage
+        | IFrameMessageAction.LedgerSignTypedData;
+    } & (
+      | {
+          success: true;
+          payload: LedgerSignMessageResponse | LedgerSignTypedDataResponse;
+        }
+      | { success: false; payload: { error: Error } }
+    ))
 );
 
-type LedgerConnectionChangeActionResponse = {
-  messageId: number;
-  action: IFrameMessageAction.LedgerConnectionChange;
-  payload: { connected: boolean };
-};
-
-type LedgerMakeAppActionResponse = {
-  messageId: number;
-  action: IFrameMessageAction.LedgerMakeApp;
-} & ({ success: true } | { success: false; error?: unknown });
-
-type LedgerUpdateTransportActionResponse = {
-  messageId: number;
-  action: IFrameMessageAction.LedgerUpdateTransport;
-  success: boolean;
-};
-
-type LedgerUnlockActionResponse = {
-  action: IFrameMessageAction.LedgerUnlock;
-} & IFrameMessageResponseStub<GetPublicKeyResponse>;
-
-type LedgerSignTransactionActionResponse = {
-  action: IFrameMessageAction.LedgerSignTransaction;
-} & IFrameMessageResponseStub<LedgerSignTransactionResponse>;
-
-type LedgerSignPersonalMessageActionResponse = {
-  action: IFrameMessageAction.LedgerSignPersonalMessage;
-} & IFrameMessageResponseStub<LedgerSignMessageResponse>;
-
-type LedgerSignTypedDataActionResponse = {
-  action: IFrameMessageAction.LedgerSignTypedData;
-} & IFrameMessageResponseStub<LedgerSignTypedDataResponse>;
-
-export type IFrameMessageResponse =
-  | LedgerConnectionChangeActionResponse
-  | LedgerMakeAppActionResponse
-  | LedgerUpdateTransportActionResponse
-  | LedgerUnlockActionResponse
-  | LedgerSignTransactionActionResponse
-  | LedgerSignPersonalMessageActionResponse
-  | LedgerSignTypedDataActionResponse;
-
 type IFrameMessage<TAction extends IFrameMessageAction> = {
   action: TAction;
   params?: Readonly<Record<string, unknown>>;
@@ -92,15 +80,17 @@ export class LedgerIframeBridge implements LedgerBridge {
 
   eventListener?: (eventMessage: {
     origin: string;
-    data: IFrameMessageResponse;
+    data: IFrameMessageResponse<IFrameMessageAction>;
   }) => void;
 
   isDeviceConnected = false;
 
   currentMessageId = 0;
 
-  messageCallbacks: Record<number, (response: IFrameMessageResponse) => void> =
-    {};
+  messageCallbacks: Record<
+    number,
+    (response: IFrameMessageResponse<IFrameMessageAction>) => void
+  > = {};
 
   delayedPromise?: {
     resolve: (value: boolean) => void;
@@ -129,12 +119,10 @@ export class LedgerIframeBridge implements LedgerBridge {
           action: IFrameMessageAction.LedgerMakeApp,
         },
         (response) => {
-          if ('success' in response && response.success) {
+          if (response.success) {
             resolve(true);
-          } else if ('error' in response) {
-            reject(response.error);
           } else {
-            reject(new Error('Unknown error occurred'));
+            reject(response.error);
           }
         },
       );
@@ -159,8 +147,8 @@ export class LedgerIframeBridge implements LedgerBridge {
           action: IFrameMessageAction.LedgerUpdateTransport,
           params: { transportType },
         },
-        (response) => {
-          if ('success' in response && response.success) {
+        ({ success }) => {
+          if (success) {
             return resolve(true);
           }
           return reject(new Error('Ledger transport could not be updated'));
@@ -235,16 +223,11 @@ export class LedgerIframeBridge implements LedgerBridge {
           action,
           params,
         },
-        (response) => {
-          if ('payload' in response && response.payload) {
-            if ('success' in response && response.success) {
-              return resolve(response.payload);
-            }
-            if ('error' in response.payload) {
-              return reject(response.payload.error);
-            }
+        ({ success, payload }) => {
+          if (success) {
+            return resolve(payload);
           }
-          return reject(new Error('Unknown error occurred'));
+          return reject(payload.error);
         },
       );
     });
@@ -284,7 +267,7 @@ export class LedgerIframeBridge implements LedgerBridge {
     bridgeUrl: string,
     eventMessage: {
       origin: string;
-      data: IFrameMessageResponse;
+      data: IFrameMessageResponse<IFrameMessageAction>;
     },
   ) {
     if (eventMessage.origin !== this.#getOrigin(bridgeUrl)) {
@@ -306,7 +289,7 @@ export class LedgerIframeBridge implements LedgerBridge {
 
   #sendMessage<TAction extends IFrameMessageAction>(
     message: IFrameMessage<TAction>,
-    callback: (response: IFrameMessageResponse) => void,
+    callback: (response: IFrameMessageResponse<TAction>) => void,
   ) {
     this.currentMessageId += 1;
 
@@ -316,7 +299,9 @@ export class LedgerIframeBridge implements LedgerBridge {
       target: LEDGER_IFRAME_ID,
     };
 
-    this.messageCallbacks[this.currentMessageId] = callback;
+    this.messageCallbacks[this.currentMessageId] = callback as (
+      response: IFrameMessageResponse<IFrameMessageAction>,
+    ) => void;
 
     if (!this.iframeLoaded || !this.iframe || !this.iframe.contentWindow) {
       throw new Error('The iframe is not loaded yet');