Angular 2 form validation pattern regex error

I'm creating a form in angular that requires the name field only contain alphanumeric characters and spaces. To do this I use the pattern attribute:

<input type="text" class="form-control" placeholder="Name" name="Name" [(ngModel)]="name" required pattern="/^[a-z\d-_\s]+$/i" #nameField="ngModel">

and I have the following error message I want to show when the string does not match:

<div *ngIf="nameField.errors">
   <div [hidden]="!nameField.errors.pattern">
       <p class="has-error">
          Only spaces, letters, and numbers are allowed.
       </p>
   </div>
</div>

However, it seems that even when the string should match the regular expression, I can still see the error message. Any ideas?