diff --git a/pkg/smartcontract/context/context_test.go b/pkg/smartcontract/context/context_test.go
index d3c62b135..a4f40cd0e 100644
--- a/pkg/smartcontract/context/context_test.go
+++ b/pkg/smartcontract/context/context_test.go
@@ -169,6 +169,12 @@ func TestParameterContext_MarshalJSON(t *testing.T) {
 	})
 }
 
+func TestSharpJSON(t *testing.T) {
+	input := []byte(`{"type":"Neo.Network.P2P.Payloads.Transaction","data":"AKTv6hJY8h4AAAAAAKwiUwEAAAAA0lEAAAFBO\u002BhSRSuucNKVX2lk7k5Wdr\u002BkOQEAMR8RwB8MEHNldEV4ZWNGZWVGYWN0b3IMFHvGgcCh9x1UNFe2i7qNX5/dTl7MQWJ9W1I=","items":{"0x39a4bf76564eee64695f95d270ae2b4552e83b41":{"script":"GwwhAwCbdUDhDyVi5f2PrJ6uwlFmpYsm5BI0j/WoaSe/rCKiDCEDAgXpzvrqWh38WAryDI1aokaLsBSPGl5GBfxiLIDmBLoMIQIUuvDO6jpm8X5\u002BHoOeol/YvtbNgua7bmglAYkGX0T/AQwhAzjSoai75eQ8YzNBYTMIaaXgqqUeYTSWGEp8xylL\u002BVafDCEDPY41\u002BM2aM4UigLbZMJPHKS7VzpDZDxSfotpQumFo384MIQI\u002BmzLqiblNBm5kmxJP1Q45bukTaejipq4bEcFw0CIlbQwhA0CNzUFjlvZHg6xYfqHhWTxX2f6ogMimoZIOkqJZR3gGDCEDScfvC0qvGB8KPhNQxSexNsxbQkmMuDq4iAwF7ZUWfhwMIQJWZM7wq8uneHrV\u002BxLzrzHFzcekeQaKoq2O54gEdov/6QwhA1tPm\u002BK4U\u002BButaCcFn4Di5a0gEI1lhUQQjJS8u49u6WDDCEDZQpoRGGmS/Rr7lYdmYGkxXrcbMvTqVErg3AUgLMCGKsMIQJqEKorTXY5xd6vpP8IFGfbELXQBDJ0mipe4dK/7SPhwAwhAn5FmyZLb34yWrSwuw\u002BmQQgftoUX/WE\u002BvXqUy3nTCB5PDCECiMrUQqh3lgx2tPaI9L4w92glbZo9okkrAYC5EkORi08MIQKkDFUnmPeWNglYF\u002ByIkk/Gy3CU5aPLBZqbO8keo78NPQwhAqeDS\u002BmzLimB0VfLW706y0LP0R6lw7ECJNekTpjFkQ8bDCECuixw9ZlvNXpDGYcFhZ\u002BuLP6hPhFyligAdys9WIqdSr0MIQLVeGqSFKij8XV9dZb9EPUkEgXiwNaDYvR2ZXm6xhiSSQwhA9jVjSJXymyxRSK3ZRPUeD99SBgBaViTeUwhhlFcbedvDCEC23nmnFGK6SVOMUtvX0tj6RTN1LJXTcL5I2wBwfwdiXMMIQLsFD8AuIUkyvNqASHC3gnu8FGd2\u002BHHEKAPDiZjIB7kwAAVQZ7Q3Do=","parameters":[{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"},{"type":"Signature"}],"signatures":{"03650a684461a64bf46bee561d9981a4c57adc6ccbd3a9512b83701480b30218ab":"QtjYFNpGOOnij\u002BLwNZLOO3fHNoVQas\u002B4\u002BAo6SdvEeP3C12ATXzgPjAZrd5mCDc3KYkce0wwveEuuoYA8mhraUA==","0288cad442a877960c76b4f688f4be30f768256d9a3da2492b0180b91243918b4f":"RmuTXfPokXWEL9RIM9DqUUsOH8iRMfrKTp6LdhdJ0KBW6rNSEuxxNOpSUMBEW1EE2CNh1c\u002BmElj2Ny3o89SzGQ==","035b4f9be2b853e06eb5a09c167e038b96b4804235961510423252f2ee3dbba583":"1VYiT\u002BPe/7syYDSOWaJ1jPyZ6JDPrdU9toDu0Cg9pRQAJW1KLSexiosLA73k7lQeVbq4YuNlWnY7U8CYIQ/ilA==","02a40c552798f79636095817ec88924fc6cb7094e5a3cb059a9b3bc91ea3bf0d3d":"/mXUPXp/tI6Y7LhudKzBE8K2soHcPgrr48YLrwgbTI4qypYpOzh\u002BNj03pkAvk8\u002B68kuefevNQb/pjmPRvs80DA=="}}},"network":877933390}`)
+	pc := ParameterContext{}
+	require.NoError(t, json.Unmarshal(input, &pc))
+}
+
 func getPrivateKeys(t *testing.T, n int) ([]*keys.PrivateKey, []*keys.PublicKey) {
 	privs := make([]*keys.PrivateKey, n)
 	pubs := make([]*keys.PublicKey, n)
diff --git a/pkg/smartcontract/context/item.go b/pkg/smartcontract/context/item.go
index 2b8a3dc57..b648b04f2 100644
--- a/pkg/smartcontract/context/item.go
+++ b/pkg/smartcontract/context/item.go
@@ -1,9 +1,7 @@
 package context
 
 import (
-	"encoding/base64"
 	"encoding/hex"
-	"encoding/json"
 
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
@@ -11,15 +9,9 @@ import (
 
 // Item represents a transaction context item.
 type Item struct {
-	Script     []byte
-	Parameters []smartcontract.Parameter
-	Signatures map[string][]byte
-}
-
-type itemAux struct {
-	Script     string                    `json:"script"`
+	Script     []byte                    `json:"script"`
 	Parameters []smartcontract.Parameter `json:"parameters"`
-	Signatures map[string]string         `json:"signatures"`
+	Signatures map[string][]byte         `json:"signatures"`
 }
 
 // GetSignature returns signature for pub if present.
@@ -32,49 +24,3 @@ func (it *Item) AddSignature(pub *keys.PublicKey, sig []byte) {
 	pubHex := hex.EncodeToString(pub.Bytes())
 	it.Signatures[pubHex] = sig
 }
-
-// MarshalJSON implements json.Marshaler interface.
-func (it Item) MarshalJSON() ([]byte, error) {
-	ci := itemAux{
-		Script:     base64.StdEncoding.EncodeToString(it.Script),
-		Parameters: it.Parameters,
-		Signatures: make(map[string]string, len(it.Signatures)),
-	}
-
-	for key, sig := range it.Signatures {
-		ci.Signatures[key] = hex.EncodeToString(sig)
-	}
-
-	return json.Marshal(ci)
-}
-
-// UnmarshalJSON implements json.Unmarshaler interface.
-func (it *Item) UnmarshalJSON(data []byte) error {
-	ci := new(itemAux)
-	if err := json.Unmarshal(data, ci); err != nil {
-		return err
-	}
-
-	script, err := base64.StdEncoding.DecodeString(ci.Script)
-	if err != nil {
-		return err
-	}
-
-	sigs := make(map[string][]byte, len(ci.Signatures))
-	for keyHex, sigHex := range ci.Signatures {
-		_, err := keys.NewPublicKeyFromString(keyHex)
-		if err != nil {
-			return err
-		}
-		sig, err := hex.DecodeString(sigHex)
-		if err != nil {
-			return err
-		}
-		sigs[keyHex] = sig
-	}
-
-	it.Signatures = sigs
-	it.Script = script
-	it.Parameters = ci.Parameters
-	return nil
-}