Ticket #31786: 31786.diff

wp-admin/custom-header.php

@@ -944 +944 @@
          * @param mixed $choice Which header image to select. Allows for values of 'random-default-image',
          *      for randomly cycling among the default images; 'random-uploaded-image', for randomly cycling
          *      among the uploaded images; the key of a default image registered for that theme; and
-         *      the key of an image uploaded for that theme (the basename of the URL).
+         *      the key of an image uploaded for that theme (the attachment ID of the image).
          *  Or an array of arguments: attachment_id, url, width, height. All are required.
          *
          * @since 3.4.0

wp-includes/theme.php

@@ -1178 +1178 @@
         foreach ( (array) $headers as $header ) {
                 $url = esc_url_raw( wp_get_attachment_url( $header->ID ) );
                 $header_data = wp_get_attachment_metadata( $header->ID );
-                $header_index = basename($url);
+                $header_index = $header->ID;
                 $header_images[$header_index] = array();
                 $header_images[$header_index]['attachment_id'] =  $header->ID;
                 $header_images[$header_index]['url'] =  $url;