diff --git a/index.js b/index.js
index 2651072..e4303ef 100644
--- a/index.js
+++ b/index.js
@@ -233,7 +233,7 @@ class WebextensionPlugin {
       }
 
       manifest = {
-            ...this.manifestDefaults,
+        ...this.manifestDefaults,
         ...manifest
       }