diff --git a/src/filesystem/Filesystem.php b/src/filesystem/Filesystem.php
--- a/src/filesystem/Filesystem.php
+++ b/src/filesystem/Filesystem.php
@@ -740,6 +740,10 @@
    * @task   directory
    */
   public static function walkToRoot($path, $root = '/') {
+    if (phutil_is_windows() && $root == '/') {
+        $root = getenv('HOMEDRIVE');
+    }
+
     $path = self::resolvePath($path);
     $root = self::resolvePath($root);