diff --git a/association.go b/association.go
index cbec41c3..a8a67be7 100644
--- a/association.go
+++ b/association.go
@@ -26,7 +26,7 @@ func (association *Association) Find(value interface{}) *Association {
 	return association.setErr(association.Scope.db.Error)
 }
 
-func (association *Association) Append(values ...interface{}) *Association {
+func (association *Association) saveAssociations(values ...interface{}) *Association {
 	scope := association.Scope
 	field := association.Field
 	relationship := association.Field.Relationship
@@ -81,6 +81,13 @@ func (association *Association) Append(values ...interface{}) *Association {
 	return association
 }
 
+func (association *Association) Append(values ...interface{}) *Association {
+	if relationship := association.Field.Relationship; relationship.Kind == "has_one" {
+		return association.Replace(values...)
+	}
+	return association.saveAssociations(values...)
+}
+
 func (association *Association) Replace(values ...interface{}) *Association {
 	var (
 		relationship = association.Field.Relationship
@@ -91,7 +98,7 @@ func (association *Association) Replace(values ...interface{}) *Association {
 
 	// Append new values
 	association.Field.Set(reflect.Zero(association.Field.Field.Type()))
-	association.Append(values...)
+	association.saveAssociations(values...)
 
 	// Belongs To
 	if relationship.Kind == "belongs_to" {
@@ -114,6 +121,10 @@ func (association *Association) Replace(values ...interface{}) *Association {
 			}
 		}
 
+		if relationship.PolymorphicDBName != "" {
+			newDB = newDB.Where(fmt.Sprintf("%v = ?", scope.Quote(relationship.PolymorphicDBName)), scope.TableName())
+		}
+
 		// Relations except new created
 		if len(values) > 0 {
 			var newPrimaryKeys [][]interface{}
diff --git a/field.go b/field.go
index db1fdd8f..6bfac0bb 100644
--- a/field.go
+++ b/field.go
@@ -42,6 +42,10 @@ func (field *Field) Set(value interface{}) error {
 			reflectValue = reflect.ValueOf(value)
 		}
 
+		if !reflectValue.IsValid() {
+			return nil
+		}
+
 		if reflectValue.Type().ConvertibleTo(field.Field.Type()) {
 			field.Field.Set(reflectValue.Convert(field.Field.Type()))
 		} else {
diff --git a/migration_test.go b/migration_test.go
index 819a378a..57d9530a 100644
--- a/migration_test.go
+++ b/migration_test.go
@@ -15,7 +15,7 @@ func runMigration() {
 		DB.Exec(fmt.Sprintf("drop table %v;", table))
 	}
 
-	values := []interface{}{&Product{}, &Email{}, &Address{}, &CreditCard{}, &Company{}, &Role{}, &Language{}, &HNPost{}, &EngadgetPost{}, &Animal{}, &User{}, &JoinTable{}, &Post{}, &Category{}, &Comment{}}
+	values := []interface{}{&Product{}, &Email{}, &Address{}, &CreditCard{}, &Company{}, &Role{}, &Language{}, &HNPost{}, &EngadgetPost{}, &Animal{}, &User{}, &JoinTable{}, &Post{}, &Category{}, &Comment{}, &Cat{}, &Dog{}, &Toy{}}
 	for _, value := range values {
 		DB.DropTable(value)
 	}
diff --git a/polymorphic_test.go b/polymorphic_test.go
index 78b99feb..f926fdd4 100644
--- a/polymorphic_test.go
+++ b/polymorphic_test.go
@@ -1,6 +1,11 @@
 package gorm_test
 
-import "testing"
+import (
+	"fmt"
+	"reflect"
+	"sort"
+	"testing"
+)
 
 type Cat struct {
 	Id   int
@@ -21,15 +26,30 @@ type Toy struct {
 	OwnerType string
 }
 
-func TestPolymorphic(t *testing.T) {
-	DB.AutoMigrate(&Cat{})
-	DB.AutoMigrate(&Dog{})
-	DB.AutoMigrate(&Toy{})
+var compareToys = func(toys []Toy, contents []string) bool {
+	var toyContents []string
+	for _, toy := range toys {
+		toyContents = append(toyContents, toy.Name)
+	}
+	sort.Strings(toyContents)
+	sort.Strings(contents)
+	return reflect.DeepEqual(toyContents, contents)
+}
 
-	cat := Cat{Name: "Mr. Bigglesworth", Toy: Toy{Name: "cat nip"}}
-	dog := Dog{Name: "Pluto", Toys: []Toy{Toy{Name: "orange ball"}, Toy{Name: "yellow ball"}}}
+func TestPolymorphic(t *testing.T) {
+	cat := Cat{Name: "Mr. Bigglesworth", Toy: Toy{Name: "cat toy"}}
+	dog := Dog{Name: "Pluto", Toys: []Toy{Toy{Name: "dog toy 1"}, Toy{Name: "dog toy 2"}}}
 	DB.Save(&cat).Save(&dog)
 
+	if DB.Model(&cat).Association("Toy").Count() != 1 {
+		t.Errorf("Cat's toys count should be 1")
+	}
+
+	if DB.Model(&cat).Association("Toy").Count() != 1 {
+		t.Errorf("Dog's toys count should be 2")
+	}
+
+	// Query
 	var catToys []Toy
 	if DB.Model(&cat).Related(&catToys, "Toy").RecordNotFound() {
 		t.Errorf("Did not find any has one polymorphic association")
@@ -46,11 +66,52 @@ func TestPolymorphic(t *testing.T) {
 		t.Errorf("Should have found all polymorphic has many associations")
 	}
 
+	var catToy Toy
+	DB.Model(&cat).Association("Toy").Find(&catToy)
+	if catToy.Name != cat.Toy.Name {
+		t.Errorf("Should find has one polymorphic association")
+	}
+
+	var dogToys1 []Toy
+	DB.Model(&dog).Association("Toys").Find(&dogToys1)
+	if !compareToys(dogToys1, []string{"dog toy 1", "dog toy 2"}) {
+		t.Errorf("Should find has many polymorphic association")
+	}
+
+	// Append
+	DB.Model(&cat).Association("Toy").Append(&Toy{
+		Name: "cat toy 2",
+	})
+
+	var catToy2 Toy
+	DB.Model(&cat).Association("Toy").Find(&catToy2)
+	if catToy2.Name != "cat toy 2" {
+		t.Errorf("Should update has one polymorphic association with Append")
+	}
+
 	if DB.Model(&cat).Association("Toy").Count() != 1 {
-		t.Errorf("Should return one polymorphic has one association")
+		t.Errorf("Cat's toys count should be 1 after Append")
 	}
 
 	if DB.Model(&dog).Association("Toys").Count() != 2 {
 		t.Errorf("Should return two polymorphic has many associations")
 	}
+
+	DB.Model(&dog).Association("Toys").Append(&Toy{
+		Name: "dog toy 3",
+	})
+
+	var dogToys2 []Toy
+	DB.Model(&dog).Association("Toys").Find(&dogToys2)
+	fmt.Println(dogToys2)
+	if !compareToys(dogToys2, []string{"dog toy 1", "dog toy 2", "dog toy 3"}) {
+		t.Errorf("Dog's toys should be updated with Append")
+	}
+
+	if DB.Model(&dog).Association("Toys").Count() != 3 {
+		t.Errorf("Should return three polymorphic has many associations")
+	}
+	// Replace
+	// Delete
+	// Clear
 }