diff --git a/lib/config.ts b/lib/config.ts
index 782a635c..3c3050c3 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -57,7 +57,7 @@ export interface ConfigSchema {
   globalNodePath: string | null,
 }
 
-export const defaultConfig = {
+export const defaultConfig = Object.freeze({
   enableSemanticRules: false,
   rulesDirectory: "",
   fixOnSave: false,
@@ -65,4 +65,4 @@ export const defaultConfig = {
   useLocalTslint: true,
   useGlobalTslint: false,
   globalNodePath: "",
-}
+} as const)
diff --git a/lib/main.ts b/lib/main.ts
index aeacd61f..a04fb051 100644
--- a/lib/main.ts
+++ b/lib/main.ts
@@ -3,12 +3,12 @@ import path from 'path';
 import { promises } from 'fs';
 const { stat } = promises;
 import { WorkerHelper } from './workerHelper';
-import { defaultConfig } from "./config"
+import { defaultConfig, ConfigSchema } from "./config"
 
 const grammarScopes = ['source.ts', 'source.tsx'];
 const editorClass = 'linter-tslint-compatible-editor';
 const idleCallbacks = new Set();
-const config = defaultConfig;
+const config: ConfigSchema = { ...defaultConfig } // copy of default config
 
 // Worker still hasn't initialized, since the queued idle callbacks are
 // done in order, waiting on a newly queued idle callback will ensure that
diff --git a/lib/worker.ts b/lib/worker.ts
index 660a9cdd..e632bfdf 100644
--- a/lib/worker.ts
+++ b/lib/worker.ts
@@ -7,6 +7,7 @@ import { getRuleUri } from 'tslint-rule-documentation';
 import ChildProcess from 'child_process';
 import getPath from 'consistent-path';
 import { shim } from "./compat-shim";
+import { defaultConfig } from "./config"
 import type { ConfigSchema } from "./config"
 import type { emit } from 'node:cluster';
 import type * as Tslint from "tslint";
@@ -17,9 +18,7 @@ process.title = 'linter-tslint worker';
 
 const tslintModuleName = 'tslint';
 const tslintCache = new Map<string, typeof Tslint.Linter>();
-const config: ConfigSchema = {
-  useLocalTslint: false,
-};
+const config: ConfigSchema = { ...defaultConfig } // copy of default config
 
 let fallbackLinter: typeof Tslint.Linter;
 let requireResolve: typeof import("resolve");
@@ -233,6 +232,7 @@ async function TsLintWorker(initialConfig: ConfigSchema) {
 
   process.on('message', async (message: JobMessage | ConfigMessage) => {
     if (message.messageType === 'config') {
+      // set the config for the worker
       config[message.message.key] = message.message.value;
 
       if (message.message.key === 'useLocalTslint') {
diff --git a/lib/workerHelper.ts b/lib/workerHelper.ts
index 66a4664a..a7492930 100644
--- a/lib/workerHelper.ts
+++ b/lib/workerHelper.ts
@@ -81,8 +81,8 @@ export class WorkerHelper {
 export type ConfigMessage = {
   messageType: 'config',
   message: {
-    key: string,
-    value: any,
+    key: keyof ConfigSchema,
+    value: boolean | string | null,
   }
 }