diff --git a/build/lib/extensions.js b/build/lib/extensions.js
index 3196f889c49..5827ee2a21c 100644
--- a/build/lib/extensions.js
+++ b/build/lib/extensions.js
@@ -208,8 +208,8 @@ const marketplaceWebExtensions = [
     'ms-vscode.references-view'
 ];
 const productJson = JSON.parse(fs.readFileSync(path.join(__dirname, '../../product.json'), 'utf8'));
-const builtInExtensions = productJson.builtInExtensions;
-const webBuiltInExtensions = productJson.webBuiltInExtensions;
+const builtInExtensions = productJson.builtInExtensions || [];
+const webBuiltInExtensions = productJson.webBuiltInExtensions || [];
 /**
  * Loosely based on `getExtensionKind` from `src/vs/workbench/services/extensions/common/extensionsUtil.ts`
  */
diff --git a/build/lib/extensions.ts b/build/lib/extensions.ts
index 88b2cf19ec0..3297c8784fd 100644
--- a/build/lib/extensions.ts
+++ b/build/lib/extensions.ts
@@ -251,8 +251,8 @@ interface IBuiltInExtension {
 }
 
 const productJson = JSON.parse(fs.readFileSync(path.join(__dirname, '../../product.json'), 'utf8'));
-const builtInExtensions: IBuiltInExtension[] = productJson.builtInExtensions;
-const webBuiltInExtensions: IBuiltInExtension[] = productJson.webBuiltInExtensions;
+const builtInExtensions: IBuiltInExtension[] = productJson.builtInExtensions || [];
+const webBuiltInExtensions: IBuiltInExtension[] = productJson.webBuiltInExtensions || [];
 
 type ExtensionKind = 'ui' | 'workspace' | 'web';
 interface IExtensionManifest {