diff --git a/src/App.php b/src/App.php
index f583f151a6..d02ea73ca4 100644
--- a/src/App.php
+++ b/src/App.php
@@ -1399,16 +1399,12 @@ class App
 			}
 		}
 
-		if (!empty($_SESSION)) {
-			$user_theme = defaults($_SESSION, 'theme', $system_theme);
-		} else {
-			$user_theme = $system_theme;
-		}
+		$user_theme = Core\Session::get('theme', $system_theme);
 
 		// Specific mobile theme override
-		if (($this->is_mobile || $this->is_tablet) && defaults($_SESSION, 'show-mobile', true)) {
+		if (($this->is_mobile || $this->is_tablet) && Core\Session::get('show-mobile', true)) {
 			$system_mobile_theme = Config::get('system', 'mobile-theme');
-			$user_mobile_theme = defaults($_SESSION, 'mobile-theme', $system_mobile_theme);
+			$user_mobile_theme = Core\Session::get('mobile-theme', $system_mobile_theme);
 
 			// --- means same mobile theme as desktop
 			if (!empty($user_mobile_theme) && $user_mobile_theme !== '---') {
diff --git a/src/Core/Session.php b/src/Core/Session.php
index b245c675b0..6d059eb4ef 100644
--- a/src/Core/Session.php
+++ b/src/Core/Session.php
@@ -45,9 +45,24 @@ class Session
 		return isset($_SESSION[$name]);
 	}
 
-	public static function get($name)
+	/**
+	 * Retrieves a key from the session super global or the defaults if the key is missing or the value is falsy.
+	 * 
+	 * Handle the case where session_start() hasn't been called and the super global isn't available.
+	 *
+	 * @param string $name
+	 * @param mixed $defaults
+	 * @return mixed
+	 */
+	public static function get($name, $defaults = null)
 	{
-		return defaults($_SESSION, $name, null);
+		if (isset($_SESSION)) {
+			$return = defaults($_SESSION, $name, $defaults);
+		} else {
+			$return = $defaults;
+		}
+
+		return $return;
 	}
 
 	public static function set($name, $value)