diff --git a/modules/@angular/forms/src/directives/ng_model.ts b/modules/@angular/forms/src/directives/ng_model.ts
index 5e32a25d77..91c1229534 100644
--- a/modules/@angular/forms/src/directives/ng_model.ts
+++ b/modules/@angular/forms/src/directives/ng_model.ts
@@ -200,7 +200,9 @@ export class NgModel extends NgControl implements OnChanges,
 
               private _updateDisabled(changes: SimpleChanges) {
                 const disabledValue = changes['isDisabled'].currentValue;
-                const isDisabled = disabledValue != null && disabledValue != false;
+
+                const isDisabled =
+                    disabledValue === '' || (disabledValue && disabledValue !== 'false');
 
                 resolvedPromise.then(() => {
                   if (isDisabled && !this.control.disabled) {
diff --git a/modules/@angular/forms/test/directives_spec.ts b/modules/@angular/forms/test/directives_spec.ts
index 877d1ec56b..15286e7b95 100644
--- a/modules/@angular/forms/test/directives_spec.ts
+++ b/modules/@angular/forms/test/directives_spec.ts
@@ -485,7 +485,7 @@ export function main() {
     });
 
     describe('NgModel', () => {
-      var ngModel: any /** TODO #9100 */;
+      let ngModel: NgModel;
 
       beforeEach(() => {
         ngModel = new NgModel(
@@ -539,6 +539,45 @@ export function main() {
 
            expect(ngModel.control.errors).toEqual({'async': true});
          }));
+
+      it('should mark as disabled properly', fakeAsync(() => {
+           ngModel.ngOnChanges({isDisabled: new SimpleChange('', undefined)});
+           tick();
+           expect(ngModel.control.disabled).toEqual(false);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange('', null)});
+           tick();
+           expect(ngModel.control.disabled).toEqual(false);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange('', false)});
+           tick();
+           expect(ngModel.control.disabled).toEqual(false);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange('', 'false')});
+           tick();
+           expect(ngModel.control.disabled).toEqual(false);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange('', 0)});
+           tick();
+           expect(ngModel.control.disabled).toEqual(false);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange(null, '')});
+           tick();
+           expect(ngModel.control.disabled).toEqual(true);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange(null, 'true')});
+           tick();
+           expect(ngModel.control.disabled).toEqual(true);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange(null, true)});
+           tick();
+           expect(ngModel.control.disabled).toEqual(true);
+
+           ngModel.ngOnChanges({isDisabled: new SimpleChange(null, 'anything else')});
+           tick();
+           expect(ngModel.control.disabled).toEqual(true);
+
+         }));
     });
 
     describe('FormControlName', () => {
diff --git a/modules/@angular/forms/test/template_integration_spec.ts b/modules/@angular/forms/test/template_integration_spec.ts
index 0af59cbfc0..271578159d 100644
--- a/modules/@angular/forms/test/template_integration_spec.ts
+++ b/modules/@angular/forms/test/template_integration_spec.ts
@@ -420,6 +420,31 @@ export function main() {
            });
          }));
 
+      it('should disable a control with unbound disabled attr', fakeAsync(() => {
+           TestBed.overrideComponent(NgModelForm, {
+             set: {
+               template: `
+            <form>
+             <input name="name" [(ngModel)]="name" disabled>
+            </form>
+          `,
+             }
+           });
+           const fixture = TestBed.createComponent(NgModelForm);
+           fixture.detectChanges();
+           tick();
+           const form = fixture.debugElement.children[0].injector.get(NgForm);
+           expect(form.control.get('name').disabled).toBe(true);
+
+           const input = fixture.debugElement.query(By.css('input'));
+           expect(input.nativeElement.disabled).toEqual(true);
+
+           form.control.enable();
+           fixture.detectChanges();
+           tick();
+           expect(input.nativeElement.disabled).toEqual(false);
+         }));
+
     });
 
     describe('radio controls', () => {