diff --git a/system/src/Grav/Common/Data/Data.php b/system/src/Grav/Common/Data/Data.php
index 76f38762e..bfae2dae8 100644
--- a/system/src/Grav/Common/Data/Data.php
+++ b/system/src/Grav/Common/Data/Data.php
@@ -26,7 +26,7 @@ class Data implements DataInterface, \ArrayAccess, \Countable, \JsonSerializable
     /** @var array */
     protected $items;
 
-    /** @var Blueprints */
+    /** @var Blueprint */
     protected $blueprints;
 
     /** @var File */
diff --git a/system/src/Grav/Common/Language/Language.php b/system/src/Grav/Common/Language/Language.php
index e83f72f7e..70a82f0cd 100644
--- a/system/src/Grav/Common/Language/Language.php
+++ b/system/src/Grav/Common/Language/Language.php
@@ -11,6 +11,7 @@ namespace Grav\Common\Language;
 
 use Grav\Common\Grav;
 use Grav\Common\Config\Config;
+use Negotiation\AcceptLanguage;
 use Negotiation\LanguageNegotiator;
 
 class Language
@@ -208,7 +209,7 @@ class Language
                     $negotiator = new LanguageNegotiator();
                     $best_language = $negotiator->getBest($accept, $this->languages);
 
-                    if ($best_language) {
+                    if ($best_language instanceof AcceptLanguage) {
                         $this->active = $best_language->getType();
                     } else {
                         $this->active = $this->getDefault();
diff --git a/system/src/Grav/Common/Page/Page.php b/system/src/Grav/Common/Page/Page.php
index adf938495..5c16bbabb 100644
--- a/system/src/Grav/Common/Page/Page.php
+++ b/system/src/Grav/Common/Page/Page.php
@@ -23,6 +23,7 @@ use Grav\Common\Taxonomy;
 use Grav\Common\Uri;
 use Grav\Common\Utils;
 use Grav\Common\Yaml;
+use Negotiation\Accept;
 use Negotiation\Negotiator;
 use RocketTheme\Toolbox\Event\Event;
 use RocketTheme\Toolbox\File\MarkdownFile;
@@ -1405,7 +1406,8 @@ class Page implements PageInterface
             $priorities = Utils::getMimeTypes($supported_types);
 
             $media_type = $negotiator->getBest($http_accept, $priorities);
-            $mimetype = $media_type ? $media_type->getValue() : '';
+            $mimetype = $media_type instanceof Accept ? $media_type->getValue() : '';
+
             $this->template_format = Utils::getExtensionByMime($mimetype);
 
             return $this->template_format;
diff --git a/tests/phpstan/phpstan.neon b/tests/phpstan/phpstan.neon
index 3e169581f..d55a66070 100644
--- a/tests/phpstan/phpstan.neon
+++ b/tests/phpstan/phpstan.neon
@@ -19,7 +19,16 @@ parameters:
         - Grav\Common\Session
     ignoreErrors:
 
-        # Errors that needs some more thinking (design...)
+        # FIXME: Bugs that need to be fixed
+
+        # TODO: Errors that needs some more thinking (bad design?)
+        - '#Access to an undefined property RocketTheme\\Toolbox\\Event\\Event::#'
+        - '#Access to an undefined property Grav\\Common\\Data\\Blueprint::#'
+        - '#Access to an undefined property Grav\\Common\\Media\\Interfaces\\MediaObjectInterface::#'
+        - '#Access to an undefined property Grav\\Common\\Page\\Interfaces\\PageInterface::#'
+        -
+            message: '#Cannot call method path\(\) on string#'
+            path: 'system/src/Grav/Common/Page/Media.php'
 
         # Needed: full coverage (probably with admin plugin...) then redesign constructor
         -
@@ -28,7 +37,7 @@ parameters:
 
         # Needed: psr-17 (http-factories) support (through decorator or further investigations)
         -
-            message: '#Call to an undefined static method Grav\\Framework\\Psr7\\Stream::create\(\).#'
+            message: '#Call to an undefined static method Grav\\Framework\\Psr7\\Stream::create\(\)#'
             path: 'system/src/Grav/Framework/Form/FormFlashFile.php'
 
         # PSR-16 Exception interfaces do not extend \Throwable
@@ -37,7 +46,7 @@ parameters:
         # Medium __call() methods
         - '#Call to an undefined method Grav\\Common\\Page\\Medium\\(\w*)Medium::#'
 
-        # Those errors are about plugins (need to find a better solution)
+        # These errors are about plugins (need to find a better solution)
         -
             message: '#Call to static method sendEmail\(\) on an unknown class Grav\\Plugin\\Email\\Utils#'
             path: 'system/src/Grav/Common/Scheduler/Job.php'
@@ -50,11 +59,11 @@ parameters:
 
         # Can be ignored, after fopen there's always an $http_response_header locally available
         -
-            message: '#Variable \$http_response_header in isset\(\) always exists and is not nullable.#'
+            message: '#Variable \$http_response_header in isset\(\) always exists and is not nullable#'
             path: 'system/src/Grav/Common/GPM/Response.php'
 
 
-        # Those errors can be ignored (they depends on installed extensions)
+        # These errors can be ignored (they depend on installed extensions)
         -
             message: '#Instantiated class (Memcache|Memcached|Redis|RedisException) not found#'
             path: 'system/src/Grav/Common/Cache.php'