Ticket #22080: 22080.3.diff

theme.php

@@ -1535 +1535 @@
                 $args = array_slice( func_get_args(), 1 );
 
         switch ( $feature ) {
+                case 'post-thumbnails':
+                        // Support has already been added for all post types and has a boolean value of true.
+                        if ( true === get_theme_support( 'post-thumbnails' ) ) {
+                                return;
+                        }
+
+                        // Get previously added post types and merge unique values into new array as args.
+                        if ( is_array( $args[0] ) && is_array( $_wp_theme_features['post-thumbnails'][0] ) ) {
+                                $values = array_unique( array_merge( $args[0], $_wp_theme_features['post-thumbnails'][0] ) );
+                                $args   = array( $values );
+                        }
+
+                        break;
+
                 case 'post-formats' :
                         if ( is_array( $args[0] ) ) {
                                 $post_formats = get_post_format_slugs();