diff --git a/windows/lib/WixSDK.js b/windows/lib/WixSDK.js
index a6e3d36..6910ac7 100644
--- a/windows/lib/WixSDK.js
+++ b/windows/lib/WixSDK.js
@@ -257,20 +257,14 @@ function(app_path, xwalk_path, meta_data, callback) {
         });
     }
 
-    // Extensions are supposed to be in the source application root dir: app_path.
-    // Then we copy them to the sub-directory of the installer folder:
-    //     app_files_folder/xwalk-extensions
-    // So, if we still fully copy the source application root directory, all the
-    // extensions will be duplicated.
-    // Extensions can be divided by categories in seperate directories.
+    // Only .dll files in extension folders will be picked up into
+    // app_files_folder/xwalk-extensions.
     this._manifest.extensions.forEach(function(extDir) {
         installExtensionDlls(extDir, app_extensions_folder);
-        if (path.normalize(path.dirname(extDir)) == path.normalize(app_path)) {
-            extensions_relative_dir.push(path.relative(app_path, extDir));
-        }
     }.bind(this));
 
     // Skip in-folder extensions copying to avoid duplication.
+    // Because the needed extension files has already be installed by previous step.
     installFiles(app_path, app_files_folder, this._manifest.extensions);
 
     var program_menu_folder_ref = product.ele('DirectoryRef', { Id: 'ApplicationProgramsFolder' });
@@ -362,11 +356,14 @@ function(app_path, xwalk_path, meta_data, callback) {
         if (success) {
             // Pass back built package
             meta_data.msi = path.resolve(basename + ".msi");
-            // Only delete on success, for debugging reasons.
-            ShellJS.rm("-f", basename + ".wxs");
-            ShellJS.rm("-f", basename + ".wixobj");
-            ShellJS.rm("-f", basename + ".wixpdb");
         }
+        // move .wxs .wixobj .wixpdb files to root_path
+        // so that they can be kept with option "-k".
+        var root_path = path.normalize(path.dirname(app_path));
+        ShellJS.mv("-f", basename + ".wxs", root_path);
+        ShellJS.mv("-f", basename + ".wixobj", root_path);
+        ShellJS.mv("-f", basename + ".wixpdb", root_path);
+
         callback(success);
     });
 };