diff --git a/goldens/public-api/common/index.md b/goldens/public-api/common/index.md
index a59371b0e2a..2b23b1ede40 100644
--- a/goldens/public-api/common/index.md
+++ b/goldens/public-api/common/index.md
@@ -403,7 +403,7 @@ export class NgClass implements DoCheck {
     // (undocumented)
     set ngClass(value: string | string[] | Set<string> | {
         [klass: string]: any;
-    });
+    } | null | undefined);
     // (undocumented)
     ngDoCheck(): void;
     // (undocumented)
diff --git a/packages/common/src/directives/ng_class.ts b/packages/common/src/directives/ng_class.ts
index 9c9d815b18d..3eb0161dca9 100644
--- a/packages/common/src/directives/ng_class.ts
+++ b/packages/common/src/directives/ng_class.ts
@@ -61,7 +61,7 @@ export class NgClass implements DoCheck {
   }
 
   @Input('ngClass')
-  set ngClass(value: string|string[]|Set<string>|{[klass: string]: any}) {
+  set ngClass(value: string|string[]|Set<string>|{[klass: string]: any}|null|undefined) {
     this._removeClasses(this._rawClass);
     this._applyClasses(this._initialClasses);
 
diff --git a/packages/common/test/directives/ng_class_spec.ts b/packages/common/test/directives/ng_class_spec.ts
index 353e2722440..19e2fe3c5e8 100644
--- a/packages/common/test/directives/ng_class_spec.ts
+++ b/packages/common/test/directives/ng_class_spec.ts
@@ -115,6 +115,17 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
            detectChangesAndExpectClassName('bar');
          }));
 
+      it('should remove active classes when expression evaluates to undefined', waitForAsync(() => {
+           fixture = createTestComponent('<div [ngClass]="objExpr"></div>');
+
+           detectChangesAndExpectClassName('foo');
+
+           getComponent().objExpr = undefined;
+           detectChangesAndExpectClassName('');
+
+           getComponent().objExpr = {'foo': false, 'bar': true};
+           detectChangesAndExpectClassName('bar');
+         }));
 
       it('should allow multiple classes per expression', waitForAsync(() => {
            fixture = createTestComponent('<div [ngClass]="objExpr"></div>');
@@ -246,6 +257,15 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
            detectChangesAndExpectClassName('');
          }));
 
+      it('should remove active classes when switching from string to undefined',
+         waitForAsync(() => {
+           fixture = createTestComponent(`<div [ngClass]="strExpr"></div>`);
+           detectChangesAndExpectClassName('foo');
+
+           getComponent().strExpr = undefined;
+           detectChangesAndExpectClassName('');
+         }));
+
       it('should take initial classes into account when switching from string to null',
          waitForAsync(() => {
            fixture = createTestComponent(`<div class="foo" [ngClass]="strExpr"></div>`);
@@ -255,6 +275,15 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
            detectChangesAndExpectClassName('foo');
          }));
 
+      it('should take initial classes into account when switching from string to undefined',
+         waitForAsync(() => {
+           fixture = createTestComponent(`<div class="foo" [ngClass]="strExpr"></div>`);
+           detectChangesAndExpectClassName('foo');
+
+           getComponent().strExpr = undefined;
+           detectChangesAndExpectClassName('foo');
+         }));
+
       it('should ignore empty and blank strings', waitForAsync(() => {
            fixture = createTestComponent(`<div class="foo" [ngClass]="strExpr"></div>`);
            getComponent().strExpr = '';
@@ -275,6 +304,9 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
 
            getComponent().objExpr = null;
            detectChangesAndExpectClassName('init foo');
+
+           getComponent().objExpr = undefined;
+           detectChangesAndExpectClassName('init foo');
          }));
 
       it('should co-operate with the interpolated class attribute', waitForAsync(() => {
@@ -289,6 +321,9 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
 
            getComponent().objExpr = null;
            detectChangesAndExpectClassName(`init foo`);
+
+           getComponent().objExpr = undefined;
+           detectChangesAndExpectClassName(`init foo`);
          }));
 
       it('should co-operate with the interpolated class attribute when interpolation changes',
@@ -315,6 +350,9 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
 
            getComponent().objExpr = null;
            detectChangesAndExpectClassName(`init foo`);
+
+           getComponent().objExpr = undefined;
+           detectChangesAndExpectClassName(`init foo`);
          }));
 
       it('should co-operate with the class attribute and class.name binding', waitForAsync(() => {
@@ -351,6 +389,9 @@ import {ComponentFixture, TestBed, waitForAsync} from '@angular/core/testing';
 
            cmp.objExpr = null;
            detectChangesAndExpectClassName('init baz');
+
+           cmp.objExpr = undefined;
+           detectChangesAndExpectClassName('init baz');
          }));
     });
 
@@ -419,8 +460,8 @@ class TestComponent {
   items: any[]|undefined;
   arrExpr: string[] = ['foo'];
   setExpr: Set<string> = new Set<string>();
-  objExpr: {[klass: string]: any}|null = {'foo': true, 'bar': false};
-  strExpr: string|null = 'foo';
+  objExpr: {[klass: string]: any}|null|undefined = {'foo': true, 'bar': false};
+  strExpr: string|null|undefined = 'foo';
 
   constructor() {
     this.setExpr.add('foo');