diff --git a/src/ol/worker/version.js b/src/ol/worker/version.js
index ef9b86ad0f..89c6106ba9 100644
--- a/src/ol/worker/version.js
+++ b/src/ol/worker/version.js
@@ -4,9 +4,12 @@
  */
 import {VERSION} from '../util.js';
 
-onmessage = event => {
+/** @type {any} */
+const worker = self;
+
+worker.onmessage = event => {
   console.log('version worker received message:', event.data); // eslint-disable-line
-  postMessage(`version: ${VERSION}`);
+  worker.postMessage(`version: ${VERSION}`);
 };
 
 export let create;
diff --git a/src/ol/worker/webgl.js b/src/ol/worker/webgl.js
index d1542aad4e..93c446aefb 100644
--- a/src/ol/worker/webgl.js
+++ b/src/ol/worker/webgl.js
@@ -10,7 +10,10 @@ import {
 } from '../renderer/webgl/Layer.js';
 import {assign} from '../obj.js';
 
-onmessage = event => {
+/** @type {any} */
+const worker = self;
+
+worker.onmessage = event => {
   const received = event.data;
   if (received.type === WebGLWorkerMessageType.GENERATE_BUFFERS) {
     const renderInstructions = new Float32Array(received.renderInstructions);
@@ -41,7 +44,7 @@ onmessage = event => {
       renderInstructions: renderInstructions.buffer
     }, received);
 
-    postMessage(message, [vertexBuffer.buffer, indexBuffer.buffer, renderInstructions.buffer]);
+    worker.postMessage(message, [vertexBuffer.buffer, indexBuffer.buffer, renderInstructions.buffer]);
   }
 };
 
diff --git a/tsconfig.json b/tsconfig.json
index 6e378a37be..438785ff84 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -3,7 +3,7 @@
     /* Basic Options */
     "target": "ES2017",                       /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
     "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
-    "lib": ["es2017", "dom", "webworker"],    /* Specify library files to be included in the compilation. */
+    "lib": ["es2017", "dom"],                 /* Specify library files to be included in the compilation. */
     "allowJs": true,                          /* Allow javascript files to be compiled. */
     "checkJs": true,                          /* Report errors in .js files. */
     // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */