diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0d829fe12..9e97dcfb3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
     * Reverted `case_insensitive_urls` option as it was causing issues with taxonomy [#1733](https://github.com/getgrav/grav/pull/1733)
     * Removed an extra `/` in `CompileFile.php` [#1693](https://github.com/getgrav/grav/pull/1693)
     * Uri: Encode user and password to prevent issues in browsers
+    * Fixed "Invalid AJAX response" When using Built-in PHP Webserver in Windows [#1258](https://github.com/getgrav/grav/issues/1258)
     
 # v1.3.8
 ## 10/26/2017
diff --git a/system/src/Grav/Common/Uri.php b/system/src/Grav/Common/Uri.php
index e87584885..473cf460e 100644
--- a/system/src/Grav/Common/Uri.php
+++ b/system/src/Grav/Common/Uri.php
@@ -249,7 +249,8 @@ class Uri
      */
     private function buildRootPath()
     {
-        $scriptPath = $_SERVER['PHP_SELF'];
+        // In Windows script path uses backslash, convert it:
+        $scriptPath = str_replace('\\', '/', $_SERVER['PHP_SELF']);
         $rootPath = str_replace(' ', '%20', rtrim(substr($scriptPath, 0, strpos($scriptPath, 'index.php')), '/'));
 
         // check if userdir in the path and workaround PHP bug with PHP_SELF