diff --git a/src/wp-includes/html-api/class-wp-html-tag-processor.php b/src/wp-includes/html-api/class-wp-html-tag-processor.php
index ab0b88693a..31352d2e88 100644
--- a/src/wp-includes/html-api/class-wp-html-tag-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-tag-processor.php
@@ -1815,6 +1815,7 @@ class WP_HTML_Tag_Processor {
 	 * For string attributes, the value is escaped using the `esc_attr` function.
 	 *
 	 * @since 6.2.0
+	 * @since 6.2.1 Fix: Only create a single update for multiple calls with case-variant attribute names.
 	 *
 	 * @param string      $name  The attribute name to target.
 	 * @param string|bool $value The new attribute value.
@@ -1907,8 +1908,8 @@ class WP_HTML_Tag_Processor {
 			 *
 			 *    Result: <div id="new"/>
 			 */
-			$existing_attribute             = $this->attributes[ $comparable_name ];
-			$this->lexical_updates[ $name ] = new WP_HTML_Text_Replacement(
+			$existing_attribute = $this->attributes[ $comparable_name ];
+			$this->lexical_updates[ $comparable_name ] = new WP_HTML_Text_Replacement(
 				$existing_attribute->start,
 				$existing_attribute->end,
 				$updated_attribute
diff --git a/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php b/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
index 6b0c263c5d..39d8fd3550 100644
--- a/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
+++ b/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
@@ -962,6 +962,24 @@ class Tests_HtmlApi_wpHtmlTagProcessor extends WP_UnitTestCase {
 		);
 	}
 
+	/**
+	 * Ensures that when setting an attribute multiple times that only
+	 * one update flushes out into the updated HTML.
+	 *
+	 * @ticket 58146
+	 *
+	 * @covers WP_HTML_Tag_Processor::set_attribute
+	 */
+	public function test_set_attribute_with_case_variants_updates_only_the_original_first_copy() {
+		$p = new WP_HTML_Tag_Processor( '<div data-enabled="5">' );
+		$p->next_tag();
+		$p->set_attribute( 'DATA-ENABLED', 'canary' );
+		$p->set_attribute( 'Data-Enabled', 'canary' );
+		$p->set_attribute( 'dATa-EnABled', 'canary' );
+
+		$this->assertSame( '<div data-enabled="canary">', strtolower( $p->get_updated_html() ) );
+	}
+
 	/**
 	 * @ticket 56299
 	 *