diff --git a/neofsid/neofsid_contract.go b/neofsid/neofsid_contract.go
index 6849010..667d009 100644
--- a/neofsid/neofsid_contract.go
+++ b/neofsid/neofsid_contract.go
@@ -18,6 +18,10 @@ type (
 	}
 )
 
+const (
+	ownerSize = 1 + interop.Hash160Len + 4
+)
+
 const (
 	netmapContractKey    = "netmapScriptHash"
 	containerContractKey = "containerScriptHash"
@@ -33,7 +37,7 @@ func _deploy(data interface{}, isUpdate bool) {
 		for iterator.Next(it) {
 			kv := iterator.Value(it).([][]byte)
 			// V2 format
-			if len(kv[0]) == 25 {
+			if len(kv[0]) == ownerSize {
 				info := std.Deserialize(kv[1]).(UserInfo)
 				key := append([]byte{ownerKeysPrefix}, kv[0]...)
 				for i := range info.Keys {
@@ -83,11 +87,11 @@ func Update(script []byte, manifest []byte, data interface{}) {
 // AddKey binds list of provided public keys to OwnerID. Can be invoked only by
 // Alphabet nodes.
 //
-// This method panics if OwnerID is not 25 byte or public key is not 33 byte long.
+// This method panics if OwnerID is not ownerSize byte or public key is not 33 byte long.
 // If key is already bound, ignores it.
 func AddKey(owner []byte, keys []interop.PublicKey) {
 	// V2 format
-	if len(owner) != 25 {
+	if len(owner) != ownerSize {
 		panic("incorrect owner")
 	}
 
@@ -147,11 +151,11 @@ func AddKey(owner []byte, keys []interop.PublicKey) {
 // RemoveKey unbinds provided public keys from OwnerID. Can be invoked only by
 // Alphabet nodes.
 //
-// This method panics if OwnerID is not 25 byte or public key is not 33 byte long.
+// This method panics if OwnerID is not ownerSize byte or public key is not 33 byte long.
 // If key is already unbound, ignores it.
 func RemoveKey(owner []byte, keys []interop.PublicKey) {
 	// V2 format
-	if len(owner) != 25 {
+	if len(owner) != ownerSize {
 		panic("incorrect owner")
 	}
 
@@ -201,10 +205,10 @@ func RemoveKey(owner []byte, keys []interop.PublicKey) {
 
 // Key method returns list of 33-byte public keys bound with OwnerID.
 //
-// This method panics if owner is not 25 byte long.
+// This method panics if owner is not ownerSize byte long.
 func Key(owner []byte) [][]byte {
 	// V2 format
-	if len(owner) != 25 {
+	if len(owner) != ownerSize {
 		panic("incorrect owner")
 	}