diff --git a/src/lib/RichText/Validator/CustomTemplateValidator.php b/src/lib/RichText/Validator/CustomTemplateValidator.php
index ce4d049c..1d7a86c0 100644
--- a/src/lib/RichText/Validator/CustomTemplateValidator.php
+++ b/src/lib/RichText/Validator/CustomTemplateValidator.php
@@ -22,20 +22,6 @@
  */
 final class CustomTemplateValidator implements ValidatorInterface
 {
-    /**
-     * Custom Tags global configuration (ibexa.richtext.custom_tags Semantic Config).
-     *
-     * @var array<string,array{template:string, is_inline:bool, icon:string, attributes:array<string, array{type: string, required: bool, default_value: mixed}>}>
-     */
-    private array $customTagsConfiguration;
-
-    /**
-     * Custom Styles global configuration (ibexa.richtext.custom_styles Semantic Config).
-     *
-     * @var array<string,array{template:string,inline:bool}>
-     */
-    private array $customStylesConfiguration;
-
     /**
      * CustomTemplateValidator constructor.
      *
@@ -43,11 +29,9 @@ final class CustomTemplateValidator implements ValidatorInterface
      * @param array<string,array{template:string, inline:bool}> $customStylesConfiguration
      */
     public function __construct(
-        array $customTagsConfiguration,
-        array $customStylesConfiguration
+        private readonly array $customTagsConfiguration,
+        private readonly array $customStylesConfiguration
     ) {
-        $this->customTagsConfiguration = $customTagsConfiguration;
-        $this->customStylesConfiguration = $customStylesConfiguration;
     }
 
     /**
@@ -76,16 +60,12 @@ public function validateDocument(DOMDocument $xmlDocument): array
                 }
 
                 if (!in_array($tagName, $configuredTemplateNames, true)) {
-                    @trigger_error(
-                        "Configuration for RichText Custom Tag or Custom Style '{$tagName}' not found. " .
-                        'Custom Tags and Custom Style configuration is required since 7.1, its lack will result in validation error in 8.x',
-                        E_USER_DEPRECATED
-                    );
+                    $errors[] = "Missing configuration for RichText CustomTag or CustomStyle: '$tagName'";
                     continue;
                 }
 
                 // Custom Styles does not have any attributes, so we can skip validation for them
-                if (isset($this->customStylesConfiguration[$tagName])) {
+                if(isset($this->customStylesConfiguration[$tagName])) {
                     continue;
                 }
 
diff --git a/tests/lib/RichText/Validator/CustomTemplateValidatorTest.php b/tests/lib/RichText/Validator/CustomTemplateValidatorTest.php
index 3a5148fd..4f3afd29 100644
--- a/tests/lib/RichText/Validator/CustomTemplateValidatorTest.php
+++ b/tests/lib/RichText/Validator/CustomTemplateValidatorTest.php
@@ -14,11 +14,9 @@
 use Symfony\Component\Yaml\Yaml;
 
 /**
- * Test RichText CustomTemplateValidator.
- *
- * @see \Ibexa\FieldTypeRichText\FieldType\RichText\CustomTemplateValidator
+ * @covers \Ibexa\FieldTypeRichText\FieldType\RichText\CustomTemplateValidator
  */
-class CustomTemplateValidatorTest extends TestCase
+final class CustomTemplateValidatorTest extends TestCase
 {
     private CustomTemplateValidator $validator;
 
@@ -127,7 +125,9 @@ public function providerForTestValidateDocument(): array
 </section>
 DOCBOOK
                 ),
-                [],
+                [
+                    "Missing configuration for RichText CustomTag or CustomStyle: 'non_existing_style'",
+                ],
             ],
             [
                 $this->createDocument(
@@ -205,6 +205,7 @@ public function providerForTestValidateDocument(): array
                 ),
                 [
                     'Missing RichText Custom Tag name',
+                    "Missing configuration for RichText CustomTag or CustomStyle: 'undefined_tag'",
                     "Missing attribute name for RichText Custom Tag 'video'",
                     "The attribute 'title' of RichText Custom Tag 'video' cannot be empty",
                     "The attribute 'width' of RichText Custom Tag 'video' cannot be empty",
@@ -214,31 +215,6 @@ public function providerForTestValidateDocument(): array
         ];
     }
 
-    /**
-     * Test that defined but not configured yet Custom Tag doesn't cause validation error.
-     */
-    public function testValidateDocumentAcceptsLegacyTags(): void
-    {
-        $document = $this->createDocument(
-            <<<DOCBOOK
-<?xml version="1.0" encoding="UTF-8"?>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink"
-         xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml"
-         xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom"
-         version="5.0-variant ezpublish-1.0">
-  <eztemplate name="undefined_tag">
-    <ezcontent>Undefined</ezcontent>
-    <ezconfig>
-      <ezvalue key="title">Test</ezvalue>
-    </ezconfig>
-  </eztemplate>
-</section>
-DOCBOOK
-        );
-
-        self::assertEmpty($this->validator->validateDocument($document));
-    }
-
     protected function createDocument(string $source): DOMDocument
     {
         $document = new DOMDocument();