diff --git a/goldens/public-api/router/index.md b/goldens/public-api/router/index.md
index 835b57f6aabd0..20b01051bdca0 100644
--- a/goldens/public-api/router/index.md
+++ b/goldens/public-api/router/index.md
@@ -133,11 +133,11 @@ export type CanActivateFn = (route: ActivatedRouteSnapshot, state: RouterStateSn
 // @public
 export interface CanDeactivate<T> {
     // (undocumented)
-    canDeactivate(component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot, nextState?: RouterStateSnapshot): Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree;
+    canDeactivate(component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot, nextState: RouterStateSnapshot): Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree;
 }
 
 // @public
-export type CanDeactivateFn<T> = (component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot, nextState?: RouterStateSnapshot) => Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree;
+export type CanDeactivateFn<T> = (component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot, nextState: RouterStateSnapshot) => Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree;
 
 // @public
 export interface CanLoad {
diff --git a/packages/router/src/models.ts b/packages/router/src/models.ts
index b03366dc7904a..8ffce766e30ef 100644
--- a/packages/router/src/models.ts
+++ b/packages/router/src/models.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {EnvironmentInjector, EnvironmentProviders, InjectionToken, NgModuleFactory, Provider, ProviderToken, Type} from '@angular/core';
+import {EnvironmentInjector, EnvironmentProviders, InjectionToken, NgModuleFactory, Provider, Type} from '@angular/core';
 import {Observable} from 'rxjs';
 
 import {DeprecatedLoadChildren} from './deprecated_load_children';
@@ -851,7 +851,7 @@ export type CanActivateChildFn = (childRoute: ActivatedRouteSnapshot, state: Rou
 export interface CanDeactivate<T> {
   canDeactivate(
       component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot,
-      nextState?: RouterStateSnapshot): Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean
+      nextState: RouterStateSnapshot): Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean
       |UrlTree;
 }
 
@@ -864,7 +864,7 @@ export interface CanDeactivate<T> {
  */
 export type CanDeactivateFn<T> =
     (component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot,
-     nextState?: RouterStateSnapshot) =>
+     nextState: RouterStateSnapshot) =>
         Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean|UrlTree;
 
 /**