diff --git a/pkg/core/native/oracle.go b/pkg/core/native/oracle.go
index 6ad40eeef..497373ebc 100644
--- a/pkg/core/native/oracle.go
+++ b/pkg/core/native/oracle.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"math"
 	"math/big"
+	"strings"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/dao"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop"
@@ -275,6 +276,9 @@ func (o *Oracle) RequestInternal(ic *interop.Context, url string, filter *string
 	if len(url) > maxURLLength || (filter != nil && len(*filter) > maxFilterLength) || len(cb) > maxCallbackLength || gas.Uint64() < 1000_0000 {
 		return ErrBigArgument
 	}
+	if strings.HasPrefix(cb, "_") {
+		return errors.New("disallowed callback method (starts with '_')")
+	}
 
 	if !ic.VM.AddGas(gas.Int64()) {
 		return ErrNotEnoughGas
diff --git a/pkg/core/native_oracle_test.go b/pkg/core/native_oracle_test.go
index 80555bb15..533f25d94 100644
--- a/pkg/core/native_oracle_test.go
+++ b/pkg/core/native_oracle_test.go
@@ -92,13 +92,13 @@ func getOracleContractState(h util.Uint160) *state.Contract {
 }
 
 func putOracleRequest(t *testing.T, h util.Uint160, bc *Blockchain,
-	url string, filter *string, userData []byte, gas int64) util.Uint256 {
+	url string, filter *string, cb string, userData []byte, gas int64) util.Uint256 {
 	var filtItem interface{}
 	if filter != nil {
 		filtItem = *filter
 	}
 	res, err := invokeContractMethod(bc, gas+50_000_000+5_000_000, h, "requestURL",
-		url, filtItem, "handle", userData, gas)
+		url, filtItem, cb, userData, gas)
 	require.NoError(t, err)
 	return res.Container
 }
@@ -114,7 +114,7 @@ func TestOracle_Request(t *testing.T) {
 	gasForResponse := int64(2000_1234)
 	var filter = "flt"
 	userData := []byte("custom info")
-	txHash := putOracleRequest(t, cs.Hash, bc, "url", &filter, userData, gasForResponse)
+	txHash := putOracleRequest(t, cs.Hash, bc, "url", &filter, "handle", userData, gasForResponse)
 
 	req, err := orc.GetRequestInternal(bc.dao, 1)
 	require.NotNil(t, req)
@@ -191,7 +191,7 @@ func TestOracle_Request(t *testing.T) {
 	t.Run("ErrorOnFinish", func(t *testing.T) {
 		const reqID = 2
 
-		putOracleRequest(t, cs.Hash, bc, "url", nil, []byte{1, 2}, gasForResponse)
+		putOracleRequest(t, cs.Hash, bc, "url", nil, "handle", []byte{1, 2}, gasForResponse)
 		_, err := orc.GetRequestInternal(bc.dao, reqID) // ensure ID is 2
 		require.NoError(t, err)
 
@@ -215,22 +215,25 @@ func TestOracle_Request(t *testing.T) {
 		require.Error(t, err)
 	})
 	t.Run("BadRequest", func(t *testing.T) {
-		var doBadRequest = func(t *testing.T, h util.Uint160, url string, filter *string, userData []byte, gas int64) {
-			txHash := putOracleRequest(t, h, bc, url, filter, userData, gas)
+		var doBadRequest = func(t *testing.T, h util.Uint160, url string, filter *string, cb string, userData []byte, gas int64) {
+			txHash := putOracleRequest(t, h, bc, url, filter, cb, userData, gas)
 			aer, err := bc.GetAppExecResults(txHash, trigger.Application)
 			require.NoError(t, err)
 			require.Equal(t, 1, len(aer))
 			require.Equal(t, vm.FaultState, aer[0].VMState)
 		}
 		t.Run("non-UTF8 url", func(t *testing.T) {
-			doBadRequest(t, cs.Hash, "\xff", nil, []byte{1, 2}, gasForResponse)
+			doBadRequest(t, cs.Hash, "\xff", nil, "", []byte{1, 2}, gasForResponse)
 		})
 		t.Run("non-UTF8 filter", func(t *testing.T) {
 			var f = "\xff"
-			doBadRequest(t, cs.Hash, "url", &f, []byte{1, 2}, gasForResponse)
+			doBadRequest(t, cs.Hash, "url", &f, "", []byte{1, 2}, gasForResponse)
 		})
 		t.Run("not enough gas", func(t *testing.T) {
-			doBadRequest(t, cs.Hash, "url", nil, nil, 1000)
+			doBadRequest(t, cs.Hash, "url", nil, "", nil, 1000)
+		})
+		t.Run("disallowed callback", func(t *testing.T) {
+			doBadRequest(t, cs.Hash, "url", nil, "_deploy", nil, 1000_0000)
 		})
 	})
 }