diff --git a/index.php b/index.php
index 69c0bc1b23..a73983b595 100644
--- a/index.php
+++ b/index.php
@@ -108,7 +108,7 @@ function checkMirror($action_obj)
 function main()
 {
     // quick check for fancy URL auto-detection support in installer.
-    if (isset($_SERVER['REDIRECT_URL']) && ((dirname($_SERVER['REQUEST_URI']) . '/check-fancy') === $_SERVER['REDIRECT_URL'])) {
+    if (isset($_SERVER['REDIRECT_URL']) && (preg_replace("/^\/$/","",(dirname($_SERVER['REQUEST_URI']))) . '/check-fancy') === $_SERVER['REDIRECT_URL']) {
         die("Fancy URL support detection succeeded. We suggest you enable this to get fancy (pretty) URLs.");
     }
     global $user, $action;