Index: src/wp-admin/includes/file.php
===================================================================
--- src/wp-admin/includes/file.php	(revision 42224)
+++ src/wp-admin/includes/file.php	(working copy)
@@ -433,31 +433,31 @@ function wp_edit_theme_plugin_file( $arg
 			switch ( $type ) {
 				case 'php':
 					$allowed_files = array_merge( $allowed_files, $theme->get_files( 'php', -1 ) );
 					break;
 				case 'css':
 					$style_files = $theme->get_files( 'css', -1 );
 					$allowed_files['style.css'] = $style_files['style.css'];
 					$allowed_files = array_merge( $allowed_files, $style_files );
 					break;
 				default:
 					$allowed_files = array_merge( $allowed_files, $theme->get_files( $type, -1 ) );
 					break;
 			}
 		}
 
-		if ( 0 !== validate_file( $real_file, $allowed_files ) ) {
+		if ( 0 !== validate_file( $file, array_keys( $allowed_files ) ) ) {
 			return new WP_Error( 'disallowed_theme_file', __( 'Sorry, that file cannot be edited.' ) );
 		}
 
 		$is_active = ( get_stylesheet() === $stylesheet || get_template() === $stylesheet );
 	} else {
 		return new WP_Error( 'missing_theme_or_plugin' );
 	}
 
 	// Ensure file is real.
 	if ( ! is_file( $real_file ) ) {
 		return new WP_Error( 'file_does_not_exist', __( 'No such file exists! Double check the name and try again.' ) );
 	}
 
 	// Ensure file extension is allowed.
 	$extension = null;