diff --git a/typo3/sysext/core/Classes/Html/RteHtmlParser.php b/typo3/sysext/core/Classes/Html/RteHtmlParser.php
index 54078c8452155023a5fe849c8f5233185cfc6ce0..a16f5e21d7d8335683d2c7d75a84b1ca1dc4b062 100644
--- a/typo3/sysext/core/Classes/Html/RteHtmlParser.php
+++ b/typo3/sysext/core/Classes/Html/RteHtmlParser.php
@@ -119,6 +119,8 @@ class RteHtmlParser extends HtmlParser implements LoggerAwareInterface
     protected function setProcessingConfiguration(array $processingConfiguration): void
     {
         $this->procOptions = $processingConfiguration;
+        $this->getKeepTags_cache = [];
+
         if (isset($this->procOptions['allowedClasses.'])) {
             $this->allowedClasses = (array)$this->procOptions['allowedClasses.'];
         } else {
diff --git a/typo3/sysext/core/Tests/Unit/Html/RteHtmlParserTest.php b/typo3/sysext/core/Tests/Unit/Html/RteHtmlParserTest.php
index f7ea24b92b27f8f339bfdf69ead48960473c8d89..40979236d58b8180dabe178963f2c547419fb7bf 100644
--- a/typo3/sysext/core/Tests/Unit/Html/RteHtmlParserTest.php
+++ b/typo3/sysext/core/Tests/Unit/Html/RteHtmlParserTest.php
@@ -754,4 +754,25 @@ final class RteHtmlParserTest extends UnitTestCase
         self::assertEquals('<figure class="table">' . CRLF . '<table>Allowed outside of p-tag</table>' . CRLF . '</figure>', $subject->transformTextForRichTextEditor('<figure class="table">' . CRLF . '<table>Allowed outside of p-tag</table>' . CRLF . '</figure>', $this->procOptions));
         self::assertEquals('<figure class="table">' . CRLF . '<table>Allowed outside of p-tag</table>' . CRLF . '<figcaption>My Logo</figcaption></figure>', $subject->transformTextForRichTextEditor('<figure class="table">' . CRLF . '<table>Allowed outside of p-tag</table>' . CRLF . '<figcaption>My Logo</figcaption></figure>', $this->procOptions));
     }
+
+    /**
+     * @test
+     */
+    public function resetsAllowTagsWhenProcessingConfigurationChanges(): void
+    {
+        $eventDispatcher = $this->createMock(EventDispatcherInterface::class);
+        $subject = new RteHtmlParser($eventDispatcher);
+        $input = '<remove>Foo</remove><keep>Bar</keep>';
+        $transformed = 'Foo<keep>Bar</keep>';
+        $result = $subject->transformTextForPersistence($input, [
+            'mode' => 'default',
+            'allowTags' => 'keep',
+        ]);
+        self::assertEquals($transformed, $result);
+        $result = $subject->transformTextForPersistence($input, [
+            'mode' => 'default',
+            'allowTags' => 'keep,remove',
+        ]);
+        self::assertEquals($input, $result);
+    }
 }