gistfile1.diff

diff --git a/core/ClassInfo.php b/core/ClassInfo.php
index 5a25a4a..c341b5f 100644
--- a/core/ClassInfo.php
+++ b/core/ClassInfo.php
@@ -153,16 +153,17 @@ class ClassInfo {
        public static function ancestry($class, $tablesOnly = false) {
                if (!is_string($class)) $class = get_class($class);
 
                $cacheKey = $class . '_' . (string)$tablesOnly;
                $parent = $class;
                if(!isset(self::$_cache_ancestry[$cacheKey])) {
                        $ancestry = array();
+                       class_exists($parent);
                        do {
                                if (!$tablesOnly || DataObject::has_own_table($parent)) {
                                        $ancestry[$parent] = $parent;
                                }
                        } while ($parent = get_parent_class($parent));
                        self::$_cache_ancestry[$cacheKey] = array_reverse($ancestry);
                }
 
                return self::$_cache_ancestry[$cacheKey];