diff --git a/pkg/vm/vm.go b/pkg/vm/vm.go
index 3e6914686..74a4057ae 100644
--- a/pkg/vm/vm.go
+++ b/pkg/vm/vm.go
@@ -759,10 +759,7 @@ func (v *VM) execute(ctx *Context, op Instruction) {
 
 	case SIZE:
 		elem := v.estack.Pop()
-		arr, ok := elem.value.Value().([]uint8)
-		if !ok {
-			panic("SIZE: item not of type []uint8")
-		}
+		arr := elem.Bytes()
 		v.estack.PushVal(len(arr))
 
 	case JMP, JMPIF, JMPIFNOT:
diff --git a/pkg/vm/vm_test.go b/pkg/vm/vm_test.go
index 2773a4bf2..f75631fb7 100644
--- a/pkg/vm/vm_test.go
+++ b/pkg/vm/vm_test.go
@@ -549,6 +549,33 @@ func TestPICKITEMByteArray(t *testing.T) {
 	assert.Equal(t, makeStackItem(2), vm.estack.Pop().value)
 }
 
+func TestSIZENoArgument(t *testing.T) {
+	prog := makeProgram(SIZE)
+	vm := load(prog)
+	vm.Run()
+	assert.Equal(t, true, vm.state.HasFlag(faultState))
+}
+
+func TestSIZEByteArray(t *testing.T) {
+	prog := makeProgram(SIZE)
+	vm := load(prog)
+	vm.estack.PushVal([]byte{0, 1})
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, makeStackItem(2), vm.estack.Pop().value)
+}
+
+func TestSIZEBool(t *testing.T) {
+	prog := makeProgram(SIZE)
+	vm := load(prog)
+	vm.estack.PushVal(false)
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, makeStackItem(1), vm.estack.Pop().value)
+}
+
 func TestSIGNNoArgument(t *testing.T) {
 	prog := makeProgram(SIGN)
 	vm := load(prog)