diff --git a/includes/Wpup/UpdateServer.php b/includes/Wpup/UpdateServer.php
index f6c6530..ea6d333 100644
--- a/includes/Wpup/UpdateServer.php
+++ b/includes/Wpup/UpdateServer.php
@@ -11,13 +11,7 @@ public function __construct($serverUrl = null, $serverDirectory = null) {
 			$serverDirectory = realpath(__DIR__ . '/../..');
 		}
 		if ( $serverUrl === null ) {
-			//Default to the current URL minus the query and "index.php".
-			$serverUrl = 'http://' . $_SERVER['HTTP_HOST'];
-			$path = $_SERVER['SCRIPT_NAME'];
-			if ( basename($path) === 'index.php' ) {
-				$path = dirname($path) . '/';
-			}
-			$serverUrl .= $path;
+			$serverUrl = self::guessServerUrl();
 		}
 
 		$this->serverUrl = $serverUrl;
@@ -26,6 +20,56 @@ public function __construct($serverUrl = null, $serverDirectory = null) {
 		$this->cache = new Wpup_FileCache($serverDirectory . '/cache');
 	}
 
+	/**
+	 * Guess the Server Url based on the current request.
+	 *
+	 * Defaults to the current URL minus the query and "index.php".
+	 *
+	 * @static
+	 *
+	 * @return string Url
+	 */
+	public static function guessServerUrl() {
+		$serverUrl = ( self::isSsl() ? 'https' : 'http' );
+		$serverUrl .= '://' . $_SERVER['HTTP_HOST'];
+		$path = $_SERVER['SCRIPT_NAME'];
+
+		if ( basename($path) === 'index.php' ) {
+			$dir = dirname($path);
+			if ( DIRECTORY_SEPARATOR === '/' ) {
+				$path = $dir . '/';
+			} else {
+				// Fix Windows
+				$path = str_replace('\\', '/', $dir);
+				//Make sure there's a trailing slash.
+				if ( substr($path, -1) !== '/' ) {
+					$path .= '/';
+				}
+			}
+		}
+
+		$serverUrl .= $path;
+		return $serverUrl;
+	}
+
+	/**
+	 * Determine if ssl is used.
+	 *
+	 * @see WP core - wp-includes/functions.php
+	 *
+	 * @return bool True if SSL, false if not used.
+	 */
+	public static function isSsl() {
+		if ( isset($_SERVER['HTTPS']) ) {
+			if ( $_SERVER['HTTPS'] == '1' || strtolower($_SERVER['HTTPS']) === 'on' ) {
+				return true;
+			}
+		} elseif ( isset($_SERVER['SERVER_PORT']) && ( '443' == $_SERVER['SERVER_PORT'] ) ) {
+			return true;
+		}
+		return false;
+	}
+
 	/**
 	 * Process an update API request.
 	 *
@@ -215,8 +259,8 @@ protected function logRequest($query) {
 			$columns = array(
 				isset($_SERVER['REMOTE_ADDR']) ? str_pad($_SERVER['REMOTE_ADDR'], 15, ' ') : '-',
 				isset($_SERVER['REQUEST_METHOD']) ? str_pad($_SERVER['REQUEST_METHOD'], 4, ' ') : '-',
-				isset($query['action']) ? $query['action'] : '-',
-				isset($query['slug'])   ? $query['slug']   : '-',
+				isset($query['action'])            ? $query['action']            : '-',
+				isset($query['slug'])              ? $query['slug']              : '-',
 				isset($query['installed_version']) ? $query['installed_version'] : '-',
 				isset($wpVersion) ? $wpVersion : '-',
 				isset($wpSiteUrl) ? $wpSiteUrl : '-',
@@ -339,10 +383,13 @@ protected function exitWithError($message = '', $httpStatus = 500) {
 	 * You can also set an argument to NULL to remove it.
 	 *
 	 * @param array $args An associative array of query arguments.
-	 * @param string $url The old URL.
+	 * @param string $url The old URL. Optional, defaults to the request url without query arguments.
 	 * @return string New URL.
 	 */
-	protected static function addQueryArg($args, $url) {
+	protected static function addQueryArg($args, $url = null ) {
+		if ( !isset($url) ) {
+			$url = self::guessServerUrl();
+		}
 		if ( strpos($url, '?') !== false ) {
 			$parts = explode('?', $url, 2);
 			$base = $parts[0] . '?';