diff --git a/core/includes/form.inc b/core/includes/form.inc
index d3aeb4577ec5baac4b1bb937f4a7227dba567dbf..1cb064e2757e7a8af3096cfd0aeb8cbb0f4c45ea 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -255,7 +255,6 @@ function template_preprocess_details(&$variables) {
       $variables['summary_attributes']['aria-controls'] = $element['#attributes']['id'];
     }
     $variables['summary_attributes']['aria-expanded'] = !empty($element['#attributes']['open']) ? 'true' : 'false';
-    $variables['summary_attributes']['aria-pressed'] = $variables['summary_attributes']['aria-expanded'];
   }
   $variables['title'] = (!empty($element['#title'])) ? $element['#title'] : '';
   // If the element title is a string, wrap it a render array so that markup
diff --git a/core/misc/details-aria.js b/core/misc/details-aria.js
index 1d0ef555586c26bea11131100ac9b20c95868a0b..c629719a3fc64404d7caedf9ace776fa024aed22 100644
--- a/core/misc/details-aria.js
+++ b/core/misc/details-aria.js
@@ -23,7 +23,6 @@
 
           $summary.attr({
             'aria-expanded': open,
-            'aria-pressed': open,
           });
         },
       );
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php
index e289fc48baa2ffe89ba1f72e2393c14433bc625d..10b597f66b4ad63dc4b6aa1abe2f08bb0105be4d 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php
@@ -134,7 +134,6 @@ public function testDetailsChildVisibility() {
 
     // Assert that both aria-expanded and aria-pressed are true.
     $this->assertEquals('true', $summary->getAttribute('aria-expanded'));
-    $this->assertEquals('true', $summary->getAttribute('aria-pressed'));
   }
 
   /**