diff --git a/lib/abstract-class.js b/lib/abstract-class.js
index aa958c5b..491b5793 100644
--- a/lib/abstract-class.js
+++ b/lib/abstract-class.js
@@ -9,7 +9,8 @@ var DEFAULT_CACHE_LIMIT = 1000;
 
 exports.AbstractClass = AbstractClass;
 
-jutil.inherits(AbstractClass, Validatable);
+AbstractClass.__proto__ = Validatable;
+AbstractClass.prototype.__proto__ = Validatable.prototype;
 jutil.inherits(AbstractClass, Hookable);
 
 /**
@@ -739,6 +740,7 @@ AbstractClass.belongsTo = function (anotherClass, params) {
     this.prototype['__finders__'][methodName] = function (id, cb) {
         anotherClass.find(id, function (err,inst) {
             if (err) return cb(err);
+            if (!inst) return cb(null, null);
             if (inst[fk] === this.id) {
                 cb(null, inst);
             } else {