diff --git a/pkg/compiler/debug_test.go b/pkg/compiler/debug_test.go
index 5e1c0346d..08d5da8f9 100644
--- a/pkg/compiler/debug_test.go
+++ b/pkg/compiler/debug_test.go
@@ -1,6 +1,7 @@
 package compiler
 
 import (
+	"encoding/json"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/internal/testserdes"
@@ -265,7 +266,7 @@ func _deploy(data interface{}, isUpdate bool) {}
 			Trusts: manifest.WildUint160s{
 				Value: []util.Uint160{},
 			},
-			Extra: nil,
+			Extra: json.RawMessage("null"),
 		}
 		require.ElementsMatch(t, expected.ABI.Methods, actual.ABI.Methods)
 		require.Equal(t, expected.ABI.Events, actual.ABI.Events)
diff --git a/pkg/core/native_management_test.go b/pkg/core/native_management_test.go
index b0ba0082a..1445fd901 100644
--- a/pkg/core/native_management_test.go
+++ b/pkg/core/native_management_test.go
@@ -481,7 +481,7 @@ func TestContractUpdate(t *testing.T) {
 		})
 	})
 
-	cs1.Manifest.Extra = "update me"
+	cs1.Manifest.Extra = []byte(`"update me"`)
 	manif1, err = json.Marshal(cs1.Manifest)
 	require.NoError(t, err)
 	cs1.UpdateCounter++
@@ -504,7 +504,7 @@ func TestContractUpdate(t *testing.T) {
 	cs1.NEF.Checksum = cs1.NEF.CalculateChecksum()
 	nef1b, err = cs1.NEF.Bytes()
 	require.NoError(t, err)
-	cs1.Manifest.Extra = "update me once more"
+	cs1.Manifest.Extra = []byte(`"update me once more"`)
 	manif1, err = json.Marshal(cs1.Manifest)
 	require.NoError(t, err)
 	cs1.UpdateCounter++
diff --git a/pkg/smartcontract/manifest/manifest.go b/pkg/smartcontract/manifest/manifest.go
index c7bbd0fe7..31a3011a4 100644
--- a/pkg/smartcontract/manifest/manifest.go
+++ b/pkg/smartcontract/manifest/manifest.go
@@ -34,7 +34,7 @@ type Manifest struct {
 	// Trusts is a set of hashes to a which contract trusts.
 	Trusts WildUint160s `json:"trusts"`
 	// Extra is an implementation-defined user data.
-	Extra interface{} `json:"extra"`
+	Extra json.RawMessage `json:"extra"`
 }
 
 // NewManifest returns new manifest with necessary fields initialized.
@@ -48,6 +48,7 @@ func NewManifest(name string) *Manifest {
 		Groups:             []Group{},
 		Permissions:        []Permission{},
 		SupportedStandards: []string{},
+		Extra:              json.RawMessage("null"),
 	}
 	m.Trusts.Restrict()
 	return m
@@ -143,11 +144,7 @@ func (m *Manifest) ToStackItem() (stackitem.Item, error) {
 	}
 	extra := stackitem.Make("null")
 	if m.Extra != nil {
-		e, err := json.Marshal(m.Extra)
-		if err != nil {
-			return nil, err
-		}
-		extra = stackitem.NewByteArray(e)
+		extra = stackitem.NewByteArray(m.Extra)
 	}
 	return stackitem.NewStruct([]stackitem.Item{
 		stackitem.Make(m.Name),
@@ -238,8 +235,6 @@ func (m *Manifest) FromStackItem(item stackitem.Item) error {
 	if err != nil {
 		return err
 	}
-	if string(extra) == "null" {
-		return nil
-	}
-	return json.Unmarshal(extra, &m.Extra)
+	m.Extra = extra
+	return nil
 }
diff --git a/pkg/smartcontract/manifest/manifest_test.go b/pkg/smartcontract/manifest/manifest_test.go
index 60a917252..4532dcbba 100644
--- a/pkg/smartcontract/manifest/manifest_test.go
+++ b/pkg/smartcontract/manifest/manifest_test.go
@@ -278,7 +278,7 @@ func TestManifestToStackItem(t *testing.T) {
 			Trusts: WildUint160s{
 				Value: []util.Uint160{{1, 2, 3}},
 			},
-			Extra: "some extra data",
+			Extra: []byte(`even not a json allowed`),
 		}
 		check(t, expected)
 	})
@@ -335,14 +335,6 @@ func TestManifest_FromStackItemErrors(t *testing.T) {
 			stackitem.NewArray([]stackitem.Item{}),
 			stackitem.NewArray([]stackitem.Item{}),
 			stackitem.Null{}}),
-		"invalid extra": stackitem.NewStruct([]stackitem.Item{
-			stackitem.NewByteArray([]byte{}),
-			stackitem.NewArray([]stackitem.Item{}),
-			stackitem.NewArray([]stackitem.Item{}),
-			stackitem.NewStruct([]stackitem.Item{stackitem.NewArray([]stackitem.Item{}), stackitem.NewArray([]stackitem.Item{})}),
-			stackitem.NewArray([]stackitem.Item{}),
-			stackitem.NewArray([]stackitem.Item{}),
-			stackitem.NewByteArray([]byte("not a json"))}),
 	}
 	for name, errCase := range errCases {
 		t.Run(name, func(t *testing.T) {