diff --git wp-includes/post-template.php wp-includes/post-template.php
index a8e4f89..6a26d80 100644
--- wp-includes/post-template.php
+++ wp-includes/post-template.php
@@ -318,6 +318,12 @@ function get_post_class( $class = '', $post_id = null ) {
 
 	$classes = array();
 
+	if ( !empty($class) ) {
+		if ( !is_array( $class ) )
+			$class = preg_split('#\s+#', $class);
+		$classes = array_merge($classes, $class);
+	}
+
 	if ( empty($post) )
 		return $classes;
 
@@ -366,12 +372,6 @@ function get_post_class( $class = '', $post_id = null ) {
 		}
 	}
 
-	if ( !empty($class) ) {
-		if ( !is_array( $class ) )
-			$class = preg_split('#\s+#', $class);
-		$classes = array_merge($classes, $class);
-	}
-
 	$classes = array_map('esc_attr', $classes);
 
 	return apply_filters('post_class', $classes, $class, $post->ID);