diff --git a/src/wp-includes/html-api/class-wp-html-processor.php b/src/wp-includes/html-api/class-wp-html-processor.php
index cce26a60c5350..856787c34bb8f 100644
--- a/src/wp-includes/html-api/class-wp-html-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-processor.php
@@ -862,6 +862,19 @@ private function step_in_body() {
 				$this->state->stack_of_open_elements->pop_until( $tag_name );
 				return true;
 
+			/*
+			 * > A start tag whose tag name is "plaintext"
+			 */
+			case '+PLAINTEXT':
+				if ( ! $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
+					$this->close_a_p_element();
+				}
+
+				$this->insert_html_element( $this->state->current_token );
+				$this->state->insertion_mode;
+				return true;
+
+
 			/*
 			 * > An end tag whose tag name is "p"
 			 */
@@ -997,7 +1010,6 @@ private function step_in_body() {
 			case 'OPTGROUP':
 			case 'OPTION':
 			case 'PARAM':
-			case 'PLAINTEXT':
 			case 'PRE':
 			case 'RB':
 			case 'RP':
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessor.php b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
index d9f1357b5c66f..51337f860302f 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessor.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
@@ -191,7 +191,6 @@ public function data_unsupported_special_in_body_tags() {
 			'OPTGROUP'  => array( 'OPTGROUP' ),
 			'OPTION'    => array( 'OPTION' ),
 			'PARAM'     => array( 'PARAM' ),
-			'PLAINTEXT' => array( 'PLAINTEXT' ),
 			'PRE'       => array( 'PRE' ),
 			'RB'        => array( 'RB' ),
 			'RP'        => array( 'RP' ),