After to upgrade angular 5 to 6

I tried to update my form : 

anguar 5 I had : 

```
 <select [ngModel]="toto" (ngModelChange)="onChange($event)" 

          <option *ngFor="let toto of totos" [ngValue]="toto.id">{{toto.libelle}}</option>

</select>

```

angular 6 I updated : 

```
 <select #oldValue="ngModel" [(ngModel)]="toto" (ngModelChange)="onChange(oldValue)" 

          <option *ngFor="let toto of totos" [ngValue]="toto.id">{{toto.libelle}}</option>
</select>

```

I got this error : 

```
compiler.js:215 Uncaught Error: Template parse errors:
There is no directive with "exportAs" set to "ngModel" (" 

```

I got `FormsModule` in my app.component.ts

What do I forget ? thank you