diff --git a/min/builder/index.php b/min/builder/index.php
index deb0fea..a3c4e2f 100644
--- a/min/builder/index.php
+++ b/min/builder/index.php
@@ -228,9 +228,6 @@ $(function () {
 $content = ob_get_clean();
 
 // setup Minify
-if (0 === stripos(PHP_OS, 'win')) {
-    Minify::setDocRoot(); // we may be on IIS
-}
 Minify::setCache(
     isset($min_cachePath) ? $min_cachePath : ''
     ,$min_cacheFileLocking
diff --git a/min/index.php b/min/index.php
index e36dfd5..501c8a0 100644
--- a/min/index.php
+++ b/min/index.php
@@ -25,8 +25,7 @@ Minify::setCache(
 
 if ($min_documentRoot) {
     $_SERVER['DOCUMENT_ROOT'] = $min_documentRoot;
-} elseif (0 === stripos(PHP_OS, 'win')) {
-    Minify::setDocRoot(); // IIS may need help
+    Minify::$isDocRootSet = true;
 }
 
 $min_serveOptions['minifierOptions']['text/css']['symlinks'] = $min_symlinks;
diff --git a/min/lib/Minify.php b/min/lib/Minify.php
index a000706..5baa181 100644
--- a/min/lib/Minify.php
+++ b/min/lib/Minify.php
@@ -59,7 +59,14 @@ class Minify {
      * @var string $importWarning
      */
     public static $importWarning = "/* See http://code.google.com/p/minify/wiki/CommonProblems#@imports_can_appear_in_invalid_locations_in_combined_CSS_files */\n";
-    
+
+    /**
+     * Has the DOCUMENT_ROOT been set in user code?
+     * 
+     * @var bool
+     */
+    public static $isDocRootSet = false;
+
     /**
      * Specify a cache object (with identical interface as Minify_Cache_File) or
      * a path to use with Minify_Cache_File.
@@ -160,6 +167,10 @@ class Minify {
      */
     public static function serve($controller, $options = array())
     {
+        if (! self::$isDocRootSet && 0 === stripos(PHP_OS, 'win')) {
+            self::setDocRoot();
+        }
+
         if (is_string($controller)) {
             // make $controller into object
             $class = 'Minify_Controller_' . $controller;
@@ -400,6 +411,7 @@ class Minify {
             require_once 'Minify/Logger.php';
             Minify_Logger::log("setDocRoot() set DOCUMENT_ROOT to \"{$_SERVER['DOCUMENT_ROOT']}\"");
         }
+        self::$isDocRootSet = true;
     }
     
     /**