diff --git a/src/Error.ts b/src/Error.ts
index aa094c0952..8ffb55232b 100644
--- a/src/Error.ts
+++ b/src/Error.ts
@@ -1,5 +1,6 @@
 /* eslint-disable camelcase */
 
+import {HttpClientResponseError} from './RequestSender.js';
 import {RawErrorType, StripeRawError} from './Types.js';
 
 export const generate = (rawStripeError: StripeRawError): StripeError => {
@@ -38,7 +39,7 @@ export class StripeError extends Error {
   readonly code?: string;
   readonly doc_url?: string;
   readonly param?: string;
-  readonly detail?: string | Error;
+  readonly detail?: string | Error | HttpClientResponseError;
   readonly statusCode?: number;
   readonly charge?: string;
   readonly decline_code?: string;
@@ -62,8 +63,7 @@ export class StripeError extends Error {
     this.headers = raw.headers;
     this.requestId = raw.requestId;
     this.statusCode = raw.statusCode;
-    // @ts-ignore
-    this.message = raw.message;
+    this.message = raw.message ?? '';
 
     this.charge = raw.charge;
     this.decline_code = raw.decline_code;
diff --git a/src/RequestSender.ts b/src/RequestSender.ts
index d69c3c0b87..d92dac1f24 100644
--- a/src/RequestSender.ts
+++ b/src/RequestSender.ts
@@ -9,6 +9,8 @@ import {
 import {
   emitWarning,
   normalizeHeaders,
+  parseHttpHeaderAsNumber,
+  parseHttpHeaderAsString,
   removeNullish,
   stringifyRequestData,
 } from './utils.js';
@@ -480,11 +482,10 @@ export class RequestSender {
 
       const requestStartTime = Date.now();
 
-      // @ts-ignore
       const requestEvent: RequestEvent = removeNullish({
         api_version: apiVersion,
-        account: headers['Stripe-Account'],
-        idempotency_key: headers['Idempotency-Key'],
+        account: parseHttpHeaderAsString(headers['Stripe-Account']),
+        idempotency_key: parseHttpHeaderAsString(headers['Idempotency-Key']),
         method,
         path,
         request_start_time: requestStartTime,
@@ -503,8 +504,7 @@ export class RequestSender {
               apiVersion,
               headers,
               requestRetries,
-              // @ts-ignore
-              res.getHeaders()['retry-after']
+              parseHttpHeaderAsNumber(res.getHeaders()['retry-after'])
             );
           } else if (options.streaming && res.getStatusCode() < 400) {
             return this._streamingResponseHandler(
@@ -542,7 +542,6 @@ export class RequestSender {
                   : RequestSender._generateConnectionErrorMessage(
                       requestRetries
                     ),
-                // @ts-ignore
                 detail: error,
               })
             );
diff --git a/src/Types.d.ts b/src/Types.d.ts
index f6ab743848..6eec55a377 100644
--- a/src/Types.d.ts
+++ b/src/Types.d.ts
@@ -5,6 +5,7 @@ import {
   HttpClientResponseInterface,
 } from './net/HttpClient.js';
 import {PlatformFunctions} from './platform/PlatformFunctions.js';
+import {HttpClientResponseError} from './RequestSender.js';
 
 export type AppInfo = {name?: string} & Record<string, unknown>;
 export type BufferedFile = {
@@ -50,7 +51,7 @@ export type RequestEvent = {
   method?: string;
   path?: string;
   request_start_time: number;
-  usage: Array<string>;
+  usage?: Array<string>;
 };
 export type RequestHeaders = Record<string, string | number | string[]>;
 export type RequestOptions = {
@@ -173,7 +174,7 @@ export type StripeRawError = {
   doc_url?: string;
   decline_code?: string;
   param?: string;
-  detail?: string | Error;
+  detail?: string | Error | HttpClientResponseError;
   charge?: string;
   payment_method_type?: string;
   payment_intent?: any;
diff --git a/src/Webhooks.ts b/src/Webhooks.ts
index fc3dec8907..633ca71834 100644
--- a/src/Webhooks.ts
+++ b/src/Webhooks.ts
@@ -47,7 +47,7 @@ type WebhookSignatureObject = {
 };
 export type WebhookObject = {
   DEFAULT_TOLERANCE: number;
-  signature: WebhookSignatureObject;
+  signature: WebhookSignatureObject | null;
   constructEvent: (
     payload: WebhookPayload,
     header: WebhookHeader,
@@ -75,7 +75,6 @@ export function createWebhooks(
 ): WebhookObject {
   const Webhook: WebhookObject = {
     DEFAULT_TOLERANCE: 300, // 5 minutes
-    // @ts-ignore
     signature: null,
     constructEvent(
       payload: WebhookPayload,
@@ -86,7 +85,7 @@ export function createWebhooks(
       receivedAt: number
     ): WebhookEvent {
       try {
-        this.signature.verifyHeader(
+        this.signature?.verifyHeader(
           payload,
           header,
           secret,
@@ -117,7 +116,7 @@ export function createWebhooks(
       cryptoProvider: CryptoProvider,
       receivedAt: number
     ): Promise<WebhookEvent> {
-      await this.signature.verifyHeaderAsync(
+      await this.signature?.verifyHeaderAsync(
         payload,
         header,
         secret,
@@ -394,7 +393,6 @@ export function createWebhooks(
       ) - details.timestamp;
 
     if (tolerance > 0 && timestampAge > tolerance) {
-      // @ts-ignore
       throw new StripeSignatureVerificationError(header, payload, {
         message: 'Timestamp outside the tolerance zone',
       });
diff --git a/src/net/FetchHttpClient.ts b/src/net/FetchHttpClient.ts
index bea479b463..251d727fcd 100644
--- a/src/net/FetchHttpClient.ts
+++ b/src/net/FetchHttpClient.ts
@@ -1,4 +1,5 @@
 import {RequestHeaders, RequestData, ResponseHeaders} from '../Types.js';
+import {parseHeadersForFetch} from '../utils.js';
 import {
   HttpClient,
   HttpClientInterface,
@@ -139,10 +140,8 @@ export class FetchHttpClient extends HttpClient implements HttpClientInterface {
       url.toString(),
       {
         method,
-        // @ts-ignore
-        headers,
-        // @ts-ignore
-        body,
+        headers: parseHeadersForFetch(headers),
+        body: typeof body === 'object' ? JSON.stringify(body) : body,
       },
       timeout
     );
diff --git a/src/stripe.core.ts b/src/stripe.core.ts
index 9263b7cf8a..3e90f2497b 100644
--- a/src/stripe.core.ts
+++ b/src/stripe.core.ts
@@ -242,8 +242,7 @@ export function createStripe(
 
           return accum;
         },
-        // @ts-ignore
-        undefined
+        {}
       );
     },
 
diff --git a/src/utils.ts b/src/utils.ts
index 005256d56e..ea6f7bdf93 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -73,14 +73,22 @@ export const makeURLInterpolator = ((): ((s: string) => UrlInterpolator) => {
   return (str: string): UrlInterpolator => {
     const cleanString = str.replace(/["\n\r\u2028\u2029]/g, ($0) => rc[$0]);
     return (outputs: Record<string, unknown>): string => {
-      return cleanString.replace(/\{([\s\S]+?)\}/g, ($0, $1) =>
-        // @ts-ignore
-        encodeURIComponent(outputs[$1] || '')
-      );
+      return cleanString.replace(/\{([\s\S]+?)\}/g, ($0, $1) => {
+        const output = outputs[$1];
+        if (isValidEncodeUriComponentType(output))
+          return encodeURIComponent(output);
+        return '';
+      });
     };
   };
 })();
 
+function isValidEncodeUriComponentType(
+  value: unknown
+): value is number | string | boolean {
+  return ['number', 'string', 'boolean'].includes(typeof value);
+}
+
 export function extractUrlParams(path: string): Array<string> {
   const params = path.match(/\{\w+\}/g);
   if (!params) {
@@ -376,3 +384,27 @@ export function concat(arrays: Array<Uint8Array>): Uint8Array {
 
   return merged;
 }
+
+export function parseHttpHeaderAsString<K extends keyof RequestHeaders>(
+  header: RequestHeaders[K]
+): string {
+  if (Array.isArray(header)) {
+    return header.join(', ');
+  }
+  return String(header);
+}
+
+export function parseHttpHeaderAsNumber<K extends keyof RequestHeaders>(
+  header: RequestHeaders[K]
+): number {
+  const number = Array.isArray(header) ? header[0] : header;
+  return Number(number);
+}
+
+export function parseHeadersForFetch(
+  headers: RequestHeaders
+): [string, string][] {
+  return Object.entries(headers).map(([key, value]) => {
+    return [key, parseHttpHeaderAsString(value)];
+  });
+}
diff --git a/test/utils.spec.ts b/test/utils.spec.ts
index 248d8ee92b..5f210dcefa 100644
--- a/test/utils.spec.ts
+++ b/test/utils.spec.ts
@@ -11,6 +11,8 @@ describe('utils', () => {
 
       expect(template({foo: '', baz: ''})).to.equal('/some/url//?ok=1');
 
+      expect(template({foo: 0, baz: 't'})).to.equal('/some/url/0/t?ok=1');
+
       expect(
         // Test encoding:
         template({foo: 'FOO', baz: '__::baz::__'})