diff --git a/package.json b/package.json
index 73cb97e5b5..8a0501fc94 100644
--- a/package.json
+++ b/package.json
@@ -62,6 +62,7 @@
     "@types/react-dom": "^17.0.0",
     "@types/resize-observer-browser": "^0.1.4",
     "@types/rimraf": "^3.0.0",
+    "@types/webpack": "^4.41.25",
     "@types/ws": "7.2.6",
     "@typescript-eslint/eslint-plugin": "^3.10.1",
     "@typescript-eslint/parser": "^3.10.1",
diff --git a/src/cli/injected/recorder.webpack.config.js b/src/cli/injected/recorder.webpack.config.js
index 237bbfaaa3..13f840931f 100644
--- a/src/cli/injected/recorder.webpack.config.js
+++ b/src/cli/injected/recorder.webpack.config.js
@@ -17,10 +17,11 @@
 const path = require('path');
 const InlineSource = require('../../server/injected/webpack-inline-source-plugin');
 
+/** @type {import('webpack').Configuration} */
 module.exports = {
   entry: path.join(__dirname, 'recorder.ts'),
-  devtool: 'source-map',
-  mode: 'development',
+  mode: process.env.NODE_ENV === 'production' ? 'production' : 'development',
+  devtool: false,
   module: {
     rules: [
       {
@@ -38,6 +39,8 @@ module.exports = {
   },
   output: {
     libraryTarget: 'var',
+    libraryExport: 'default',
+    library: 'pwExport',
     filename: 'recorderSource.js',
     path: path.resolve(__dirname, '../../../lib/server/injected/packed')
   },
diff --git a/src/debug/injected/consoleApi.webpack.config.js b/src/debug/injected/consoleApi.webpack.config.js
index 68425ec480..9595fa0111 100644
--- a/src/debug/injected/consoleApi.webpack.config.js
+++ b/src/debug/injected/consoleApi.webpack.config.js
@@ -17,10 +17,11 @@
 const path = require('path');
 const InlineSource = require('../../server/injected/webpack-inline-source-plugin');
 
+/** @type {import('webpack').Configuration} */
 module.exports = {
   entry: path.join(__dirname, 'consoleApi.ts'),
-  devtool: 'source-map',
-  mode: 'development',
+  mode: process.env.NODE_ENV === 'production' ? 'production' : 'development',
+  devtool: false,
   module: {
     rules: [
       {
@@ -38,6 +39,8 @@ module.exports = {
   },
   output: {
     libraryTarget: 'var',
+    library: 'pwExport',
+    libraryExport: 'default',
     filename: 'consoleApiSource.js',
     path: path.resolve(__dirname, '../../../lib/server/injected/packed')
   },
diff --git a/src/server/dom.ts b/src/server/dom.ts
index 83b58d99a7..ada660e059 100644
--- a/src/server/dom.ts
+++ b/src/server/dom.ts
@@ -82,9 +82,12 @@ export class FrameExecutionContext extends js.ExecutionContext {
       for (const [name, { source }] of this.frame._page.selectors._engines)
         custom.push(`{ name: '${name}', engine: (${source}) }`);
       const source = `
-        new (${injectedScriptSource.source})([
+        (() => {
+        ${injectedScriptSource.source}
+        return new pwExport([
           ${custom.join(',\n')}
-        ])
+        ]);
+        })();
       `;
       this._injectedScriptPromise = this._delegate.rawEvaluate(source).then(objectId => new js.JSHandle(this, 'object', objectId));
     }
diff --git a/src/server/injected/injectedScript.ts b/src/server/injected/injectedScript.ts
index aeac733c96..ee8c173ab1 100644
--- a/src/server/injected/injectedScript.ts
+++ b/src/server/injected/injectedScript.ts
@@ -146,7 +146,11 @@ export class InjectedScript {
   }
 
   extend(source: string, params: any): any {
-    const constrFunction = global.eval(source);
+    const constrFunction = global.eval(`
+    (() => {
+      ${source}
+      return pwExport;
+    })()`);
     return new constrFunction(this, params);
   }
 
diff --git a/src/server/injected/injectedScript.webpack.config.js b/src/server/injected/injectedScript.webpack.config.js
index dc4a08a986..16ecd22a54 100644
--- a/src/server/injected/injectedScript.webpack.config.js
+++ b/src/server/injected/injectedScript.webpack.config.js
@@ -16,11 +16,11 @@
 
 const path = require('path');
 const InlineSource = require('./webpack-inline-source-plugin.js');
-
+/** @type {import('webpack').Configuration} */
 module.exports = {
   entry: path.join(__dirname, 'injectedScript.ts'),
-  devtool: 'source-map',
-  mode: 'development',
+  mode: process.env.NODE_ENV === 'production' ? 'production' : 'development',
+  devtool: false,
   module: {
     rules: [
       {
@@ -38,6 +38,9 @@ module.exports = {
   },
   output: {
     filename: 'injectedScriptSource.js',
+    libraryTarget: 'var',
+    libraryExport: 'default',
+    library: 'pwExport',
     path: path.resolve(__dirname, '../../../lib/server/injected/packed')
   },
   plugins: [
diff --git a/src/server/injected/utilityScript.webpack.config.js b/src/server/injected/utilityScript.webpack.config.js
index c58f303071..5102617e50 100644
--- a/src/server/injected/utilityScript.webpack.config.js
+++ b/src/server/injected/utilityScript.webpack.config.js
@@ -17,10 +17,11 @@
 const path = require('path');
 const InlineSource = require('./webpack-inline-source-plugin.js');
 
+/** @type {import('webpack').Configuration} */
 module.exports = {
   entry: path.join(__dirname, 'utilityScript.ts'),
-  devtool: 'source-map',
-  mode: 'development',
+  mode: process.env.NODE_ENV === 'production' ? 'production' : 'development',
+  devtool: false,
   module: {
     rules: [
       {
@@ -38,6 +39,8 @@ module.exports = {
   },
   output: {
     libraryTarget: 'var',
+    library: 'pwExport',
+    libraryExport: 'default',
     filename: 'utilityScriptSource.js',
     path: path.resolve(__dirname, '../../../lib/server/injected/packed')
   },
diff --git a/src/server/injected/webpack-inline-source-plugin.js b/src/server/injected/webpack-inline-source-plugin.js
index d587d732a8..cca3b4d310 100644
--- a/src/server/injected/webpack-inline-source-plugin.js
+++ b/src/server/injected/webpack-inline-source-plugin.js
@@ -22,15 +22,12 @@ module.exports = class InlineSource {
     this.outFile = outFile;
   }
 
+  /**
+   * @param {import('webpack').Compiler} compiler
+   */
   apply(compiler) {
     compiler.hooks.emit.tapAsync('InlineSource', (compilation, callback) => {
-      let source = compilation.assets[path.basename(this.outFile).replace('.ts', '.js')].source();
-      const lastLine = source.split('\n').pop();
-      if (lastLine.startsWith('//# sourceMappingURL'))
-        source = source.substring(0, source.length - lastLine.length - 1);
-      if (source.endsWith(';'))
-        source = source.substring(0, source.length - 1);
-      source = '(' + source + ').default';
+      const source = compilation.assets[path.basename(this.outFile).replace('.ts', '.js')].source();
       fs.mkdirSync(path.dirname(this.outFile), { recursive: true });
       const newSource = 'export const source = ' + JSON.stringify(source) + ';';
       fs.writeFileSync(this.outFile, newSource);
diff --git a/src/server/javascript.ts b/src/server/javascript.ts
index e3e92bb02e..298c086a78 100644
--- a/src/server/javascript.ts
+++ b/src/server/javascript.ts
@@ -64,7 +64,11 @@ export class ExecutionContext {
 
   utilityScript(): Promise<JSHandle<UtilityScript>> {
     if (!this._utilityScriptPromise) {
-      const source = `new (${utilityScriptSource.source})()`;
+      const source = `
+      (() => {
+        ${utilityScriptSource.source}
+        return new pwExport();
+      })();`;
       this._utilityScriptPromise = this._delegate.rawEvaluate(source).then(objectId => new JSHandle(this, 'object', objectId));
     }
     return this._utilityScriptPromise;
diff --git a/test/page-evaluate.spec.ts b/test/page-evaluate.spec.ts
index b28c1c5ff9..e53e31cc52 100644
--- a/test/page-evaluate.spec.ts
+++ b/test/page-evaluate.spec.ts
@@ -554,3 +554,7 @@ it('should not use toJSON in jsonValue', async ({ page }) => {
   const resultHandle = await page.evaluateHandle(() => ({ toJSON: () => 'string', data: 'data' }));
   expect(await resultHandle.jsonValue()).toEqual({ data: 'data', toJSON: {} });
 });
+
+it('should not expose the injected script export', async ({ page }) => {
+  expect(await page.evaluate('typeof pwExport === "undefined"')).toBe(true);
+});
diff --git a/utils/build/build.js b/utils/build/build.js
index 00902353ab..693bf98966 100644
--- a/utils/build/build.js
+++ b/utils/build/build.js
@@ -40,7 +40,10 @@ function runWatch() {
 
   const spawns = [];
   for (const step of steps)
-    spawns.push(child_process.spawn(step.command, step.args, { stdio: 'inherit', shell: step.shell }));
+    spawns.push(child_process.spawn(step.command, step.args, { stdio: 'inherit', shell: step.shell, env: {
+      ...process.env,
+      ...step.env,
+    } }));
   process.on('exit', () => spawns.forEach(s => s.kill()));
   for (const onChange of onChanges)
     runOnChanges(onChange.inputs, onChange.script);
@@ -72,8 +75,11 @@ const webPackFiles = [
 for (const file of webPackFiles) {
   steps.push({
     command: 'npx',
-    args: ['webpack', '--config', filePath(file), ...(watchMode ? ['--watch', '--silent', '--mode', 'development'] : [])],
+    args: ['webpack', '--config', filePath(file), ...(watchMode ? ['--watch', '--silent'] : [])],
     shell: true,
+    env: {
+      NODE_ENV: watchMode ? 'development' : 'production'
+    }
   });
 }