diff --git a/aio/tools/stackblitz-builder/builder.js b/aio/tools/stackblitz-builder/builder.js
index 35ad2b2745..00da191c95 100644
--- a/aio/tools/stackblitz-builder/builder.js
+++ b/aio/tools/stackblitz-builder/builder.js
@@ -221,9 +221,7 @@ class StackblitzBuilder {
 
   _encodeBase64(file) {
     // read binary data
-    var bitmap = fs.readFileSync(file);
-    // convert binary data to base64 encoded string
-    return Buffer(bitmap).toString('base64');
+    return fs.readFileSync(file, { encoding: 'base64' });
   }
 
   _existsSync(filename) {