diff --git a/pkg/vm/vm.go b/pkg/vm/vm.go
index ba14f3700..1b3d93004 100644
--- a/pkg/vm/vm.go
+++ b/pkg/vm/vm.go
@@ -694,7 +694,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		}
 		s := v.estack.Pop().Bytes()
 		if t := len(s); l > t {
-			l = t
+			panic("size is too big")
 		}
 		v.estack.PushVal(NewBufferItem(s[:l]))
 
diff --git a/pkg/vm/vm_test.go b/pkg/vm/vm_test.go
index cb14a0fa7..d7a1666ef 100644
--- a/pkg/vm/vm_test.go
+++ b/pkg/vm/vm_test.go
@@ -1814,7 +1814,7 @@ func TestLEFT(t *testing.T) {
 	t.Run("NoString", getTestFuncForVM(prog, nil, 2))
 	t.Run("NegativeLen", getTestFuncForVM(prog, nil, "abcdef", -1))
 	t.Run("Good", getTestFuncForVM(prog, NewBufferItem([]byte("ab")), "abcdef", 2))
-	t.Run("GoodBigLen", getTestFuncForVM(prog, NewBufferItem([]byte("abcdef")), "abcdef", 8))
+	t.Run("BadBigLen", getTestFuncForVM(prog, nil, "abcdef", 8))
 }
 
 func TestRIGHT(t *testing.T) {