diff --git a/pkg/vm/vm.go b/pkg/vm/vm.go
index 0211ce79e..df645ad21 100644
--- a/pkg/vm/vm.go
+++ b/pkg/vm/vm.go
@@ -1087,11 +1087,11 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		validateMapKey(key)
 
 		obj := v.estack.Pop()
-		index := int(key.BigInt().Int64())
 
 		switch t := obj.value.(type) {
 		// Struct and Array items have their underlying value as []Item.
 		case *stackitem.Array, *stackitem.Struct:
+			index := int(key.BigInt().Int64())
 			arr := t.Value().([]stackitem.Item)
 			if index < 0 || index >= len(arr) {
 				panic("PICKITEM: invalid index")
@@ -1105,6 +1105,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 			}
 			v.estack.PushItem(t.Value().([]stackitem.MapElement)[index].Value.Dup())
 		default:
+			index := int(key.BigInt().Int64())
 			arr := obj.Bytes()
 			if index < 0 || index >= len(arr) {
 				panic("PICKITEM: invalid index")
diff --git a/pkg/vm/vm_test.go b/pkg/vm/vm_test.go
index 63ca28fd1..0395f813d 100644
--- a/pkg/vm/vm_test.go
+++ b/pkg/vm/vm_test.go
@@ -1205,6 +1205,16 @@ func TestSETITEMMap(t *testing.T) {
 	m := stackitem.NewMap()
 	m.Add(stackitem.Make(5), stackitem.Make(3))
 	runWithArgs(t, prog, []byte{0, 1}, m, 5, m, 5, []byte{0, 1})
+
+	t.Run("big key", func(t *testing.T) {
+		m := stackitem.NewMap()
+		key := make([]byte, stackitem.MaxKeySize)
+		for i := range key {
+			key[i] = 0x0F
+		}
+		m.Add(stackitem.NewByteArray(key), stackitem.Make(3))
+		runWithArgs(t, prog, "value", m, key, m, key, "value")
+	})
 }
 
 func TestSETITEMBigMapBad(t *testing.T) {