diff --git a/lib/validator.js b/lib/validator.js
index 2f3ef63..9aaa276 100644
--- a/lib/validator.js
+++ b/lib/validator.js
@@ -205,6 +205,11 @@ Validator.prototype.validateSchema = function validateSchema (instance, schema,
     return this.validateSchema(instance, resolved.subschema, options, subctx);
   }
 
+  // Set default value if instance is undefined and default is defined
+  if(options.setDefaults && typeof instance === 'undefined' && schema.required !== true) {
+      result.instance = instance = schema.default;
+  }
+  
   var skipAttributes = options && options.skipAttributes || [];
   // Validate each schema attribute against the instance
   for (var key in schema) {
diff --git a/test/attributes.js b/test/attributes.js
index b29154b..093395c 100644
--- a/test/attributes.js
+++ b/test/attributes.js
@@ -295,6 +295,30 @@ describe('Attributes', function () {
       return this.validator.validate({'the_field':'bar'}, {'type': 'object', 'properties':{'the_field': {'enum': ['foo', 'bar', 'baz'], 'required': true}}}).valid.should.be.true;
     });
   });
+  
+  describe('default', function () {
+    beforeEach(function () {
+      this.validator = new Validator();
+    });
+    
+    it('should preserve value if field is defined', function () {
+      var validation = this.validator.validate({'the_field': 'foo'}, {'type': 'object', 'properties':{'the_field':{'type': 'string', 'default': 'bar'}}}, {setDefaults: true});
+      validation.valid.should.be.true; 
+      validation.instance.the_field.should.equal('foo');
+    });
+    
+    it('should not set default value even field is undefined if options.setDefaults is not true', function () {
+      var validation = this.validator.validate({}, {'type': 'object', 'properties':{'the_field':{'type': 'string', 'default': 'bar'}}});
+      validation.valid.should.be.true; 
+      validation.instance.should.not.have.property('the_field');
+    });
+    
+    it('should set default value if field is undefined and options.setDefaults is true', function () {
+      var validation = this.validator.validate({}, {'type': 'object', 'properties':{'the_field':{'type': 'string', 'default': 'bar'}}}, {setDefaults: true})
+      validation.valid.should.be.true; 
+      validation.instance.the_field.should.equal('bar');
+    });
+  });
 
   describe('description', function () {
     beforeEach(function () {