diff --git a/Classes/Form/FormDataProvider/RichtextEncoreConfiguration.php b/Classes/Form/FormDataProvider/RichtextEncoreConfiguration.php
index 188d2e8..119b837 100644
--- a/Classes/Form/FormDataProvider/RichtextEncoreConfiguration.php
+++ b/Classes/Form/FormDataProvider/RichtextEncoreConfiguration.php
@@ -15,24 +15,17 @@
 use Ssch\Typo3Encore\Asset\EntrypointLookupCollectionInterface;
 use Ssch\Typo3Encore\Asset\EntrypointLookupInterface;
 use TYPO3\CMS\Backend\Form\FormDataProviderInterface;
-use TYPO3\CMS\Core\Information\Typo3Version;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 
 final class RichtextEncoreConfiguration implements FormDataProviderInterface
 {
     private EntrypointLookupCollectionInterface $entrypointLookupCollection;
 
-    private int $majorVersion = 12;
-
-    public function __construct(
-        EntrypointLookupCollectionInterface $entrypointLookupCollection = null,
-        Typo3Version $typo3Version = null
-    ) {
+    public function __construct(EntrypointLookupCollectionInterface $entrypointLookupCollection = null)
+    {
         $this->entrypointLookupCollection = $entrypointLookupCollection ?? GeneralUtility::makeInstance(
             EntrypointLookupCollection::class
         );
-        $typo3Version = $typo3Version ?? GeneralUtility::makeInstance(Typo3Version::class);
-        $this->majorVersion = $typo3Version->getMajorVersion();
     }
 
     public function addData(array $result): array
@@ -52,32 +45,26 @@ public function addData(array $result): array
             if (! isset($rteConfiguration['editor']['config']['contentsCss'])) {
                 continue;
             }
-            $contentsCss = $rteConfiguration['editor']['config']['contentsCss'];
-
-            if (is_array($contentsCss) && $this->majorVersion < 12) {
-                $updatedContentCss = [];
-                foreach ($contentsCss as $cssFile) {
-                    $updatedContent = $this->getContentCss($cssFile);
-                    $updatedContentCss[] = is_array($updatedContent) ? $updatedContent : [$updatedContent];
-                }
-                $contentsCss = array_merge(...$updatedContentCss);
-            } elseif (is_string($contentsCss)) {
-                $contentsCss = $this->getContentCss($contentsCss);
+            $contentsCss = (array) $rteConfiguration['editor']['config']['contentsCss'];
+
+            $updatedContentCss = [];
+            foreach ($contentsCss as $cssFile) {
+                $updatedContent = $this->getContentCss($cssFile);
+                $updatedContentCss[] = is_array($updatedContent) ? $updatedContent : [$updatedContent];
             }
+            $contentsCss = array_merge(...$updatedContentCss);
+
             $result['processedTca']['columns'][$fieldName]['config']['richtextConfiguration']['editor']['config']['contentsCss'] = $contentsCss;
         }
 
         return $result;
     }
 
-    /**
-     * @return array|string
-     */
-    private function getContentCss(string $contentsCss)
+    private function getContentCss(string $contentsCss): array
     {
         if (! str_starts_with($contentsCss, 'typo3_encore:')) {
             // keep the css file as-is
-            return ($this->majorVersion < 12) ? [$contentsCss] : $contentsCss;
+            return [$contentsCss];
         }
 
         // strip prefix
@@ -96,10 +83,7 @@ private function getContentCss(string $contentsCss)
         // call reset() to allow multiple RTEs on the same page.
         // Otherwise only the first RTE will have the CSS.
         $entryPointLookup->reset();
-        if ($this->majorVersion < 12) {
-            return $cssFiles;
-        }
-        // TYPO3 12 support only one css file. See https://forge.typo3.org/issues/99327
-        return reset($cssFiles);
+
+        return $cssFiles;
     }
 }
diff --git a/composer.json b/composer.json
index 1ae4583..5d74bea 100644
--- a/composer.json
+++ b/composer.json
@@ -20,17 +20,17 @@
   "minimum-stability": "dev",
   "require": {
     "php": ">=7.4",
-    "typo3/cms-core": "^10.4.2 || ^11.5 || ^12",
+    "typo3/cms-core": "^10.4.2 || ^11.5 || ^12.4",
     "symfony/web-link": "^5.4 || ^6",
     "symfony/asset": "^5.0 || ^6",
     "ext-dom": "*",
-    "typo3/cms-tstemplate": "^10.4.2 || ^11.2 || ^12",
+    "typo3/cms-tstemplate": "^10.4.2 || ^11.5 || ^12.4",
     "webmozart/assert": "^1.10"
   },
   "require-dev": {
     "phpstan/phpstan": "^1.0",
     "typo3/testing-framework": "^6.2 || dev-main",
-    "typo3/minimal": "^10.4 || ^11.5 || ^12.0",
+    "typo3/minimal": "^10.4 || ^11.5 || ^12.4",
     "php-parallel-lint/php-parallel-lint": "^1.3",
     "phpspec/prophecy-phpunit": "^2.0",
     "rector/rector": "^0.15.2",
@@ -42,7 +42,7 @@
     "saschaegerer/phpstan-typo3": "^1.8.0",
     "symplify/easy-coding-standard": "^11.0",
     "phpstan/phpstan-strict-rules": "^1.4.4",
-    "typo3/cms-rte-ckeditor": "^10.4 || ^11.5 || ^12.0"
+    "typo3/cms-rte-ckeditor": "^10.4 || ^11.5 || ^12.4"
   },
   "replace": {
     "typo3-ter/typo3-encore": "self.version"
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 5435b79..20bb3f9 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -16,44 +16,19 @@ parameters:
 			path: Classes/Asset/TagRenderer.php
 
 		-
-			message: "#^Strict comparison using \\!\\=\\= between '' and '1' will always evaluate to true\\.$#"
-			count: 1
-			path: Classes/Middleware/AssetsMiddleware.php
-
-		-
-			message: "#^Only booleans are allowed in a negated boolean, mixed given\\.$#"
-			count: 1
-			path: Classes/ViewHelpers/Stimulus/ActionViewHelper.php
-
-		-
-			message: "#^Only booleans are allowed in \\|\\|, mixed given on the left side\\.$#"
+			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
 			count: 1
-			path: Classes/ViewHelpers/Stimulus/ActionViewHelper.php
+			path: Classes/Form/FormDataProvider/RichtextEncoreConfiguration.php
 
 		-
-			message: "#^Only booleans are allowed in \\|\\|, mixed given on the right side\\.$#"
+			message: "#^Else branch is unreachable because ternary operator condition is always true\\.$#"
 			count: 1
-			path: Classes/ViewHelpers/Stimulus/ActionViewHelper.php
+			path: Classes/Form/FormDataProvider/RichtextEncoreConfiguration.php
 
 		-
-			message: "#^Only booleans are allowed in a negated boolean, mixed given\\.$#"
-			count: 1
-			path: Classes/ViewHelpers/Stimulus/ControllerViewHelper.php
-
-		-
-			message: "#^Only booleans are allowed in an if condition, mixed given\\.$#"
-			count: 1
-			path: Classes/ViewHelpers/Stimulus/ControllerViewHelper.php
-
-		-
-			message: "#^Only booleans are allowed in a negated boolean, mixed given\\.$#"
-			count: 1
-			path: Classes/ViewHelpers/Stimulus/TargetViewHelper.php
-
-		-
-			message: "#^Only booleans are allowed in an if condition, mixed given\\.$#"
+			message: "#^Strict comparison using \\!\\=\\= between '' and '1' will always evaluate to true\\.$#"
 			count: 1
-			path: Classes/ViewHelpers/Stimulus/TargetViewHelper.php
+			path: Classes/Middleware/AssetsMiddleware.php
 
 		-
 			message: "#^Only booleans are allowed in an if condition, mixed given\\.$#"