Ticket #40764: 40764.2.diff

src/wp-admin/includes/ajax-actions.php

@@ -3485 +3485 @@
         $status     = array(
                 'update'     => 'theme',
                 'slug'       => $stylesheet,
+                'oldVersion' => '',
                 'newVersion' => '',
         );
 
@@ -3493 +3494 @@
                 wp_send_json_error( $status );
         }
 
+        $theme = wp_get_theme( $stylesheet );
+
+        if ( $theme->exists() ) {
+                $status['oldVersion'] = $theme->get('Version');
+        }
+
         include_once( ABSPATH . 'wp-admin/includes/class-wp-upgrader.php' );
 
         $current = get_site_transient( 'update_themes' );