diff --git a/src/environments.ts b/src/environments.ts
deleted file mode 100644
index 4f34efa..0000000
--- a/src/environments.ts
+++ /dev/null
@@ -1,9 +0,0 @@
-/**
- * This file was auto-generated by Fern from our API Definition.
- */
-
-export const SquidexEnvironment = {
-    Default: "https://cloud.squidex.io",
-} as const;
-
-export type SquidexEnvironment = typeof SquidexEnvironment.Default;
diff --git a/src/wrapper/SquidexClient.ts b/src/wrapper/SquidexClient.ts
index 7929bc6..74e31dd 100644
--- a/src/wrapper/SquidexClient.ts
+++ b/src/wrapper/SquidexClient.ts
@@ -1,4 +1,3 @@
-import * as environments from "../environments";
 import {
     AppsApi,
     AppsApiInterface,
@@ -69,12 +68,12 @@ export interface SquidexOptions {
     /**
      * Custom headers to be added to each request.
      */
-    customHeader?: Record<string, string>;
+    customHeaders?: Record<string, string>;
 
     /**
      * The URL to your Squidex installation (cloud by default).
      */
-    environment?: environments.SquidexEnvironment | string;
+    url?: string;
 
     /**
      * A custom fetcher for normal requests.
@@ -240,8 +239,8 @@ export class SquidexClients {
     /**
      * The current URL to the Squidex installation.
      */
-    public get environment() {
-        return this.clientOptions.environment || environments.SquidexEnvironment.Default;
+    public get url() {
+        return this.clientOptions.url!;
     }
 
     constructor(readonly clientOptions: SquidexOptions) {
@@ -257,6 +256,10 @@ export class SquidexClients {
             throw new Error("Configuration 'appName' is required.");
         }
 
+        clientOptions.url ||= 'https://cloud.squidex.io';
+
+        Object.freeze(clientOptions);
+
         this.tokenStore = this.clientOptions.tokenStore || new InMemoryTokenStore();
 
         const fetchCore = this.clientOptions.fetcher || fetch;
@@ -303,7 +306,7 @@ export class SquidexClients {
         };
 
         const parameters: ConfigurationParameters = {
-            basePath: clientOptions.environment || "https://cloud.squidex.io",
+            basePath: clientOptions.url || "https://cloud.squidex.io",
             fetchApi,
         };
 
@@ -330,8 +333,8 @@ function addOptions(init: RequestInit, clientOptions: SquidexOptions) {
         init.signal = AbortSignal.timeout(clientOptions.timeout);
     }
 
-    if (clientOptions.customHeader) {
-        for (const [key, value] of Object.entries(clientOptions.customHeader)) {
+    if (clientOptions.customHeaders) {
+        for (const [key, value] of Object.entries(clientOptions.customHeaders)) {
             addHeader(init, key, value);
         }
     }
diff --git a/tests/_utils.ts b/tests/_utils.ts
index f7d49b0..9169865 100644
--- a/tests/_utils.ts
+++ b/tests/_utils.ts
@@ -14,7 +14,7 @@ export function getClient() {
     const appName = getEnvironment("CONFIG__APP__NAME", "integrations-tests");
     const clientId = getEnvironment("CONFIG__CLIENT__ID", "root");
     const clientSecret = getEnvironment("CONFIG__CLIENT__SECRET", "xeLd6jFxqbXJrfmNLlO2j1apagGGGSyZJhFnIuHp4I0=");
-    const environment = getEnvironment("CONFIG__SERVER__URL", "https://localhost:5001");
+    const url = getEnvironment("CONFIG__SERVER__URL", "https://localhost:5001");
 
     const middleware: SquidexOptions["middleware"] = {
         pre: async (params) => {
@@ -32,7 +32,7 @@ export function getClient() {
         appName,
         clientId,
         clientSecret,
-        environment,
+        url,
         middleware,
     });
 
@@ -41,7 +41,7 @@ export function getClient() {
             appName: app,
             clientId,
             clientSecret,
-            environment,
+            url,
             middleware,
         });
     };