diff --git a/core/Core.php b/core/Core.php
index 39d8632e9..ca042157a 100755
--- a/core/Core.php
+++ b/core/Core.php
@@ -134,7 +134,10 @@ if(!defined('BASE_URL')) {
 	// If that didn't work, failover to the old syntax.  Hopefully this isn't necessary, and maybe
 	// if can be phased out?
 	if(!defined('BASE_URL')) {
-		define('BASE_URL', rtrim(dirname(dirname($_SERVER['SCRIPT_NAME'])), DIRECTORY_SEPARATOR));
+		$dir = strpos($_SERVER['SCRIPT_NAME'], 'index.php')
+			? dirname($_SERVER['SCRIPT_NAME'])
+			: dirname(dirname($_SERVER['SCRIPT_NAME']));
+		define('BASE_URL', rtrim($dir, DIRECTORY_SEPARATOR));
 	}
 }
 define('MODULES_DIR', 'modules');
diff --git a/main.php b/main.php
index cb7a04645..bfa7b7e6e 100644
--- a/main.php
+++ b/main.php
@@ -107,7 +107,7 @@ require_once("core/model/DB.php");
 // Redirect to the installer if no database is selected
 if(!isset($databaseConfig) || !isset($databaseConfig['database']) || !$databaseConfig['database']) {
 	$s = (isset($_SERVER['SSL']) || (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off')) ? 's' : '';
-	$installURL = "http$s://" . $_SERVER['HTTP_HOST'] . dirname(dirname($_SERVER['SCRIPT_NAME'])) . '/install.php';
+	$installURL = "http$s://" . $_SERVER['HTTP_HOST'] . BASE_URL . '/install.php';
 	
 	// The above dirname() will equate to "\" on Windows when installing directly from http://localhost (not using
 	// a sub-directory), this really messes things up in some browsers. Let's get rid of the backslashes