diff --git a/fields_mask_test.go b/fields_mask_test.go
index 7209c2c..d1064d3 100644
--- a/fields_mask_test.go
+++ b/fields_mask_test.go
@@ -3,7 +3,7 @@ package meta_test
 import (
 	"testing"
 
-	"git.bit5.ru/backend/meta/v3"
+	"git.bit5.ru/backend/meta/v4"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
diff --git a/go.mod b/go.mod
index 5b286be..c3ada7a 100644
--- a/go.mod
+++ b/go.mod
@@ -1,4 +1,4 @@
-module git.bit5.ru/backend/meta/v3
+module git.bit5.ru/backend/meta/v4
 
 go 1.20
 
diff --git a/interface.go b/interface.go
index 42c4ba9..954b58f 100644
--- a/interface.go
+++ b/interface.go
@@ -69,6 +69,7 @@ type Readable interface {
 type Writable interface {
 	Write(Writer) error
 	WriteFields(Writer) error
+	FieldsCount() int
 }
 
 type Struct interface {
@@ -77,7 +78,7 @@ type Struct interface {
 	Writable
 }
 
-type StructFactory func(classId uint32) (Struct, error)
+type StructFactory func(classId uint32) (Readable, error)
 
 type Bitmasked interface {
 	FieldChanged(index uint64) bool
@@ -85,3 +86,8 @@ type Bitmasked interface {
 	HasChangedFields() bool
 	FieldsMask() FieldsMask
 }
+
+type WritableClass interface {
+	Class
+	Writable
+}
diff --git a/meta.go b/meta.go
index 8f84c57..573a8d0 100644
--- a/meta.go
+++ b/meta.go
@@ -1,6 +1,6 @@
 package meta
 
-func ReadStructGeneric(r Reader, createStruct StructFactory, field string) (Struct, error) {
+func ReadGeneric(r Reader, createFunc StructFactory, field string) (Readable, error) {
 	if err := r.BeginContainer(field); err != nil {
 		return nil, err
 	}
@@ -10,12 +10,12 @@ func ReadStructGeneric(r Reader, createStruct StructFactory, field string) (Stru
 		return nil, err
 	}
 
-	s, err := createStruct(classId)
+	s, err := createFunc(classId)
 	if err != nil {
 		return nil, err
 	}
 
-	if err := s.Read(r); err != nil {
+	if err := s.ReadFields(r); err != nil {
 		return nil, err
 	}
 
@@ -26,14 +26,14 @@ func ReadStructGeneric(r Reader, createStruct StructFactory, field string) (Stru
 	return s, nil
 }
 
-func WriteStructGeneric(w Writer, s Struct, field string) error {
-	if err := w.BeginCollection(2, field); err != nil {
+func WriteGeneric(w Writer, s WritableClass, field string) error {
+	if err := w.BeginCollection(s.FieldsCount()+1, field); err != nil {
 		return err
 	}
 	if err := w.WriteUint32(s.ClassId(), ""); err != nil {
 		return err
 	}
-	if err := s.Write(w); err != nil {
+	if err := s.WriteFields(w); err != nil {
 		return err
 	}
 	return w.EndCollection()
diff --git a/msgpack_assoc_writer_test.go b/msgpack_assoc_writer_test.go
index 1855ce9..0162fc9 100644
--- a/msgpack_assoc_writer_test.go
+++ b/msgpack_assoc_writer_test.go
@@ -5,7 +5,7 @@ import (
 	"encoding/hex"
 	"testing"
 
-	"git.bit5.ru/backend/meta/v3"
+	"git.bit5.ru/backend/meta/v4"
 	"github.com/stretchr/testify/require"
 )
 
diff --git a/msgpack_reader_test.go b/msgpack_reader_test.go
index 732f194..12931cd 100644
--- a/msgpack_reader_test.go
+++ b/msgpack_reader_test.go
@@ -5,7 +5,7 @@ import (
 	"encoding/hex"
 	"testing"
 
-	"git.bit5.ru/backend/meta/v3"
+	"git.bit5.ru/backend/meta/v4"
 	"github.com/stretchr/testify/require"
 )
 
diff --git a/msgpack_writer_test.go b/msgpack_writer_test.go
index 1aaaccb..5c02cd9 100644
--- a/msgpack_writer_test.go
+++ b/msgpack_writer_test.go
@@ -5,7 +5,7 @@ import (
 	"encoding/hex"
 	"testing"
 
-	"git.bit5.ru/backend/meta/v3"
+	"git.bit5.ru/backend/meta/v4"
 	"github.com/stretchr/testify/require"
 )
 
diff --git a/structs_test.go b/structs_test.go
index 18bcb2b..d6ee4ca 100644
--- a/structs_test.go
+++ b/structs_test.go
@@ -1,7 +1,7 @@
 package meta_test
 
 import (
-	"git.bit5.ru/backend/meta/v3"
+	"git.bit5.ru/backend/meta/v4"
 )
 
 type TestParent struct {