diff --git a/system/src/Grav/Common/Language/Language.php b/system/src/Grav/Common/Language/Language.php
index 74a13656e..173a4a7d6 100644
--- a/system/src/Grav/Common/Language/Language.php
+++ b/system/src/Grav/Common/Language/Language.php
@@ -174,23 +174,23 @@ class Language
 
         // if languages set
         if ($this->enabled()) {
-            // try setting from prefix of URL (/en/blah/blah)
+            // Try setting language from prefix of URL (/en/blah/blah).
             if (preg_match($regex, $uri, $matches)) {
                 $this->lang_in_url = true;
                 $this->active = $matches[2];
-                $uri = preg_replace("/\\" . $matches[1] . "/", '', $uri, 1);
+                $uri = preg_replace("/\\" . $matches[1] . '/', '', $uri, 1);
 
-                // store in session if different
-                if ($this->config->get('system.session.enabled', false)
+                // Store in session if language is different.
+                if (isset($this->grav['session']) && $this->grav['session']->started()
                     && $this->config->get('system.languages.session_store_active', true)
                     && $this->grav['session']->active_language != $this->active
                 ) {
                     $this->grav['session']->active_language = $this->active;
                 }
             } else {
-                // try getting from session, else no active
-                if ($this->config->get('system.session.enabled', false) &&
-                    $this->config->get('system.languages.session_store_active', true)) {
+                // Try getting language from the session, else no active.
+                if (isset($this->grav['session']) && $this->grav['session']->started()
+                    && $this->config->get('system.languages.session_store_active', true)) {
                     $this->active = $this->grav['session']->active_language ?: null;
                 }
                 // if still null, try from http_accept_language header
@@ -203,8 +203,8 @@ class Language
                         }
                     }
 
-                    // repeat if not found, try base language only - fixes Safari sending the language code always
-                    // with a locale (e.g. it-it or fr-fr)
+                    // Repeat if not found, try base language only - fixes Safari sending the language code always
+                    // with a locale (e.g. it-it or fr-fr).
                     foreach ($preferred as $lang) {
                         $lang = substr($lang, 0, 2);
                         if ($this->validate($lang)) {
diff --git a/system/src/Grav/Common/Service/MessagesServiceProvider.php b/system/src/Grav/Common/Service/MessagesServiceProvider.php
index f51e89a8d..9309e87f2 100644
--- a/system/src/Grav/Common/Service/MessagesServiceProvider.php
+++ b/system/src/Grav/Common/Service/MessagesServiceProvider.php
@@ -8,6 +8,8 @@
 
 namespace Grav\Common\Service;
 
+use Grav\Common\Debugger;
+use Grav\Common\Session;
 use Pimple\Container;
 use Pimple\ServiceProviderInterface;
 use RocketTheme\Toolbox\Session\Message;
@@ -18,6 +20,15 @@ class MessagesServiceProvider implements ServiceProviderInterface
     {
         // Define session message service.
         $container['messages'] = function ($c) {
+            if (!isset($c['session']) || !$c['session']->started()) {
+                /** @var Debugger $debugger */
+                $debugger = $c['debugger'];
+                $debugger->addMessage('Session not started: session messages may disappear', 'warming');
+
+                return new Message;
+            }
+
+            /** @var Session $session */
             $session = $c['session'];
 
             if (!isset($session->messages)) {