diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index 9effbadcd5..feec9b3de4 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -2607,16 +2607,19 @@ function add_theme_support( $feature, ...$args ) {
 
 		case 'html5':
 			// You can't just pass 'html5', you need to pass an array of types.
-			if ( empty( $args[0] ) ) {
-				// Build an array of types for back-compat.
-				$args = array( 0 => array( 'comment-list', 'comment-form', 'search-form' ) );
-			} elseif ( ! isset( $args[0] ) || ! is_array( $args[0] ) ) {
+			if ( empty( $args[0] ) || ! is_array( $args[0] ) ) {
 				_doing_it_wrong(
 					"add_theme_support( 'html5' )",
 					__( 'You need to pass an array of types.' ),
 					'3.6.1'
 				);
-				return false;
+
+				if ( ! empty( $args[0] ) && ! is_array( $args[0] ) ) {
+					return false;
+				}
+
+				// Build an array of types for back-compat.
+				$args = array( 0 => array( 'comment-list', 'comment-form', 'search-form' ) );
 			}
 
 			// Calling 'html5' again merges, rather than overwrites.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 290dfa1543..21c7d411db 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.0-alpha-52827';
+$wp_version = '6.0-alpha-52828';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.